TRIUMF
Non UBC
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TRIUMF brown reports TRI-69-9
Wright Engineers Limited
Arthur D. Little, Inc.
This report of the conceptual design study of the vacuum pumping system for the TRIUMF cyclotron considers two different pumping systems in detail: large trapped oil diffusion pumps, and 20°K cryopumps with auxiliary trapped oil diffusion pumps. The pumping systems are compared in relation to certain criteria. These include an equivalent nitrogen stripping cross-section pressure of 7 x 10- 8 Torr within 15 hours of pumping, minimum contamination of the vacuum chamber, and compatibility with other cyclotron components. Reliability, maintenance and test requirements have received particular attention, since cryopumping has not been widely used as a pumping method for an accelerator. The report contains a discussion of outgassing rate data of materials and an analysis of the gas loads for the cyclotron. Gauging and leak-testing methods for the vacuum chamber and pumping system are described. Estimates of capital and annual operating costs for the two pumping systems are provided, and a construction schedule concludes the report.
TRIUMF CONCEPTUAL DESIGN STUDY FOR ' THE VACUUM PUMPING SYSTEM FOR A 500 MEV H- CYCLOTRON Wright Engineers Limited, Vancouver, B.C., Arthur D. Little, Inc. Cambridge, Mass., MESON FACILITY OF: UNIVERSITY OF ALBERTA SIMON FRASER UNIVERSITY UNIVERSITY OF VICTORIA UNIVERSITY OF BRITISH COLUMBIA and TRIUMF TRl-69-9 Prepared by R.G. Blakely TRIUMF CONCEPTUAL DESIGN STUDY OF THE VACUUM PUMPING SYSTEM FOR A 500 MeV H- CYCLOTRON Wright Engineers Limited Vancouver, B.C. TRl-69-9 (Sections 8, 9, 10.2, 10.3, R.W. Moore, Jr. Vivienne J. Harwood Postal Address: TRIUMF University of British Columbia Vancouver 8, B.C. Canada 10.4, 10.5, 12, 13, 14, 15 and 16) Arthur D. Little, Inc. Cambridge, Mass. (Section 10.1) TRIUMF, UBC (Sections 1-7 and 11) August 1969 ABSTRACT This report of the conceptual design study of the vacuum pumping system for the TRIUMF cyclotron considers two different pumping systems in detail: large trapped oil diffusion pumps, and 20°K cryopumps with auxiliary trapped oil diffusion pumps. The pumping systems are compared in relation to certain criteria. These include an equivalent nitrogen stripping cross-section pressure of 7 x 10- 8 Torr within 15 hours of pumping, minimum contamination of the vacuum chamber, and compatibility with other cyclotron components. Reliability, maintenance and test requirements have received particular attention, since cryopumping has not been widely used as a pumping method for an accelerator. The report contains a discussion of outgassing rate data of materials and an analysis of the gas loads for the cyclotron. Gauging and leak-testing methods for the vacuum chamber and pumping system are described. Estimates of capital and annual operating costs for the two pumping systems are provided, and a construction schedule concludes the report. ii C O N T E N T S 1 . INTRODUCTION 2. CRITERIA FOR THE VACUUM PUMPING SYSTEM 2. 1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2. 10 Pumpdown Time Gas Density Requirements Contamination Space Limitations Compatibility Maintenance Upset Conditions Radiation Damage Instrumentation Magnetic Shielding 3. RESIDUAL GAS DENSITY AND COMPOSITION 4. GAS LOADS AND BAKEOUT 5, CONDUCTANCE OF VACUUM CHAMBER AND RESONATORS 6. PUMPING SPEEDS 7, SURVEY OF VARIOUS TYPES OF PUMPS 7,1 Turbomolecular Pump 8. 7.2 Titanium Sublimation Pump 7.3 Sputter-Ion Pump 7.4 Cryosorption Pump 7.5 Cryopumps Operating at or below 4.2°K ROUGHING SYSTEM 8. 1 Description 8. 1. 1 8. 1.2 8. 1.3 8. 1 .4 8. l .5 8. 1 .6 Rough Rough Rough Rough Rough Build of Pumping Components ng Pumps ng Line Trap ng System Valves ng Line ng System Exhaust ng Requirements 8.2 Instrumentation and Controls 8.3 Maintenance Requirements 8.4 Test Requirements 8.5 Operation and Performance 8.6 Cost Estimates iii Page 2 2 2 2 2 2 2 3 3 3 4 5 6 14 15 16 16 17 19 20 21 22 22 22 22 22 23 23 23 24 24 24 24 25 9. 32 IN. DIFFUSION PUMP SYSTEM 9.1 Description of Stack Components 9. 1. 1 Diffusion Pumps 9. 1.2 Diffusion Pump Traps 9.1.3 Isolation Valves 9. 1 .4 Backing System 9.1.5 Refrigeration for Diffusion Pump Cold Traps 9.1.6 Building Requirements 9.2 Instrumentation and Controls 9.3 Maintenance Requirements 9.4 Test Requirements 9,5 Operation and Performance 10. 20°K - 80°K CRYOPUMPED SYSTEM 10. 1 C ryopumps 10. 1. 1 Cryoarray Concepts 10.1.1.1 10. 1. 1.2 10.1. 1.3 10.1.1.4 10.1. 1.5 Cryo 1 i ne Flat-Shield Array Test Requirements Re 1 i ab i 1 i ty Cost Estimates 10. 1.2 20°K Coolant Circuit 10. 1 .3 10. 1 .4 10.1 .2. 1 10. 1 .2. 2 1 0. 1. 2. 3 10. 1 .2.4 1 O. 1. 2. 5 VJMLI Transfer Line VJLNS Transfer Line Circuit Cooldown Time Loss of 20°K Refrigeration Accidental Air Inrush 80°K Coolant Circuit 10 .1.3. 1 10. 1 .3.2 10. 1. 3.3 10. 1 .3.4 10. 1 ,3.5 10. 1. 3.6 VJR Transfer Line VJSF Transfer Line Bulk Insulated Transfer Line Circuit Cooldown Time Loss of 80°K Refrigeration Accidental Air Inrush Operating Procedures 10. 1 .4. 1 10. 1 .4.2 10.1.4. 3 Cooldown Periodic Defrost Maintenance 10.2 Cryogenic Generators 10.2. 1 Cryogenerator Configuration Configuration I Configuration I I Configurationslll and IV ConfigurationsV and VI iv Page 26 26 26 26 26 26 27 28 29 30 30 32 34 34 34 34 38 40 40 41 41 42 44 46 47 47 48 49 50 51 52 53 53 54 54 54 54 56 57 59 62 62 62 10.3 10.4 10.5 10.2.2 10.2.3 10.2.4 10.2.5 10.2.6 Instrumentation and Controls Maintenance Requirements Test Requirements Operation and Performance Cost Estimates and Suppliers Alternative Concepts Considered 10.3 .1 10. 3 .2 10. 3 .3 10.3.4 Cryogenerator Located in Vault Use of 20°K Refrigerator as a Helium Liquefier Use of Liquid Nitrogen Machine Liquid Helium for Stand-by Refrigeration at 20°K Auxiliary Diffusion Pump System 10.4.1 10.4.2 10.4.3 10.4.4 10.4.5 10.4.6 Description of Stack Components Instrumentation and Controls Maintenance Requirements Test Requirements Operation and Performance Cost Estimates and Suppliers Cost Estimates for Cryopumped Systems 11. MAIN CHAMBER GAUGING 12. DRY GAS SOURCE 13. LEAK TESTING 13.l 13.2 13 .3 Leak Testing Requirements General Leak Testing Procedure Leak Testing Techniques 13.3 .1 13.3.2 Equipment Required Sequence of Leak Tests 13.4 Comments on Leak Testing Page 65 67 68 68 70 70 70 73 74 75 76 76 78 78 78 78 80 81 84 85 87 87 87 88 89 89 90 14. CONSTRUCTION SCHEDULE 92 15. COMPARISON OF CRYOPUMPED AND DIFFUSION PUMPED SYSTEMS 94 16. RECOMMENDATIONS 98 Acknowledgements References Figures V 99 100 101 I. II. 111. IV. V. VI. VII. VI 11. IX. X. XI. XII. X 111. XIV. xv. XV I. XVI I. XV 111. XIX. xx. XXI. LIST OF TABLES Outgassing Rate Design Values Gas Load After 15 Hours Pressure Calculation Summary After Pumping Time of 15 Hours for Cryopumping System Pressure Calculation Summary After Pumping Time of 15 Hours for Diffusion Pumping System Pressure Analysis Summary Constants for Equations (3), (4) and (5) Building Requirements of Roughing System Economic Comparison of 80°K Systems for 3211 Cold Traps Building Requirements of 3211 Diffusion Pump System Emergency Procedures Diffusion Pump System Cryoline Characteristics Flat-Shield Array Characteristics VJMLI 20°K Transfer Line Characteristics VJLNS 20°K Transfer Line Characteristics 20°K Circuit Cooldown Time VJR 80°K Transfer Line Characteristics VJSF 80°K Transfer Line Characteristics Bulk Insulated 80°K Transfer Line Characteristics Alternative Cryosystem Configurations Building Requirements of Components of Configuration I Building Requirements of Components of Configurations I I I and IV vi Page 7 9 10 11 13 14 23 28 29 31 36 39 42 45 46 49 50 52 58 61 63 XXI I. XXI 11. XXIV. XXV. XXV I.XXVI . XXVI 11. XXIX. XXX. XXXI. Building Requirements of Components of Configurations V and VI Performance of Refrigeration Systems Capital Cost of Refrigeration Equipment Annual Operating Cost of Refrigeration Equipment Building Requirements of Auxiliary Diffusion Pump System Emergency Procedures Auxiliary Diffusion Pump System Capital Cost of Cryopumped Systems Annual Operating Cost of Cryopumped Systems Construction Schedule Comparison of Cryopumped and Diffusion Pumped Systems vii Page 66 69 71 72 77 79 82 83 93 95 LI ST OF FI GU RES l. Sources of Gas Load for Half the Chamber 2. Gas Load During Pumpdown 3. Schematic of Roughing System Components - Cryosystem 4. Cryopump System - Plot of Chamber Pressure versus Pumping Ti me 5. 3211 Diffusion Pump System - Plot of Chamber Pressure versus Pumping Time 6. Overall Dimensions 3211 Diffusion Pumps 7. Schematic of Diffusion Pump Stacks - 3211 Diffusion Pump System 8. Schematic of Backing System Components - Diffusion Pump System 9. Diffusion Pump System - Refrigeration for Cold Traps 10. Cross-Section - Cryoline Concept 11. Cross-Section - Flat-Shield Array Concept 12. Cross-Section - Chevron Array Concept 13. Effect of H20 Deposit on Absorptance 14. Schematic Diagram - Cryoline Positions 15. Schematic Diagram - Flat-Shield Array Positions 16. Schematic Diagram - 20°K Coolant Circuit 17. Preliminary Configuration - VJMLI 20°K He Gas Transfer Line 18. Construction of VJMLI Transfer Line 19. Cross-Section - VJLNS Transfer Line 20. Bayonet Coupling - VJLNS Transfer Line 21. Schematic Diagram - 80°K Coolant Circuit 22. Preliminary Configuration - VJR 80°K Circuit Transfer Line viii 23. Construction of VJSF Transfer Line 24. Preliminary Configuration - VJSF 80°K Circuit Transfer Line 25. 80°K Transfer Line Bulk Insulation Concept 26. Configuration I - Schematic of Refrigeration System 27. VJLNS Transfer Line for Configuration 28. Proposed Location of LN2 Tank 29. Configurations I I I and IV - Schematic of Refrigeration System 30. Configurations V and VI - Schematic of Refrigeration System 31. Refrigeration System for Combined 80°K and 20°K Loads 32. Refrigeration System for Generation of 20°K within Vault 33. Modification of Airco C Refrigeration for Liquefaction of Helium for Experimental Use 34. Schematic of LHe Storage to Provide Standby Refrigeration at 20°K 35. Cryosystem - Auxiliary Diffusion Pump Schematic 36. Cryosystem - Refrigeration for Diffusion Pump Cold Traps 37. Overall Dimensions 10'' Diffusion Pump Stacks 38. Schematic Dry Air Supply 39. Leak Rate versus Chamber Pressure 40. Configuration for Dynamic Helium Mass Spectrometer Leak Test, with Roughing System 41. Configuration for Static Helium Mass Spectrometer Leak Test, with Roughing System 42. Configuration for Dynamic Helium Mass Spectrometer Leak Test, with Diffusion Pumps ix 1 . I NT RO DUCT I ON The design of the TRIUMF cyclotron is influenced in a major way by the level of radiation which can be tolerated in the vicinity of the accelerator. The activation of the H- cyclotron occurs through two loss mechanisms: (1) stripping of the electrons of the H- ions by coll is ions with residual gas molecules in the cyclotron; and (2) elec-tric dissociation from the v x B electric field seen by the H- ions (v being the velocity of the ions and B the magnetic field strength). The most serious radiation hazards arise from the fast neutrons produced by the lost beam. The number of fast neutrons produced by a single lost H- ion is approximately proportional to the ion's energy, so it is reasonable to assume that both the total fast neutron flux and the .residual activity will be proportional to the power dissipated by the lost beam. The power dissipated in a certain energy interval may be expressed as a percentage of the potential final power of the injected beam; this is called the percentage beam power loss. The magnetic field strength has been chosen to limit the percentage beam power loss due to electric dissociation to 12%, when integrated over energy. For an operating "pressure"* of 7 x 1 o-8 Torr of nitrogen, the percentage beam power loss by gas stripping is 3.2% when inte-grated over energy, thereby enabling the total beam power loss to be limited to 10 kW for 100 µA of extracted beam at 500 MeV. Since gas stripping is spread fairly uniformly from 1 to 500 MeV, the percentage of the initial current which is lost by this process is considerably greater than 3.2%; namely, 7.4%. Thus, to extract a beam of 100 µA at 500 MeV, it is necessary to start with 124 µA, of which 15 µA are lost by electric stripping and 9 µA are lost by gas stripping. The design figure of 10 kW maximum beam power loss gives an estimated 5 R/hour activity at shutdown, which is comparable to the induced activity per unit area in existing machines. For beam energies of 400 MeV and less, the percentage beam power loss from electric dissociation is very small. The extracted beam can rise to 750 µA for a total beam power loss of 10 kW by gas stripping at 7 x 10- 8 Torr of nitrogen. When the extracted beam current is limited by other factors such as RF beam loading and stripping foil design, operating pressures of 7 x 10- 8 Torr and less will significantly reduce the level of induced activity in the cyclotron. It is the purpose of this study to investigate means by which a gas density equivalent to a pressure of 7 x 10- 8 Torr of nitrogen or less can be maintained. -~ "Throughout the report the term "pressure" will be used, since this is conventional practice. However, gas density is a more appropriate term at the concentration levels of importance, especially since the beam loss is determined by the density and nature of the specific residual gaseous components. - 2 -2. CRITERIA FOR THE VACUUM PUMPING SYSTEM 2. 1 Pumpdown Time The pumpdown time is not to exceed 15 hours from atmospheric to operating pressure after exposure of the vacuum chamber for several days to the vault atmosphere with the lid raised. 2.2 Gas Density Requirements 2.3 Beam loss by gas stripping depends on both the density and H-stripping cross-section of different gases which constitute the gas load. The sum of the products of partial pressure along the centre line of the resonators of the cyclotron and stripping cross-section of the residual gas is to be less than the same product for 7 x 10-s Torr of nitrogen. Since water vapour (mass 18), nitrogen and carbon monoxide (mass 28h hydrogen (mass 2) and carbon dioxide (mass 44) form the major constituents of the residual gas load, the following relationship can be used as the pressure criteria: 0.1 P2 + 0.61 P18 + 1.0 P28 + 1 .6 P44 7 X 10-S ( 1) where P2 is the partial pressure of mass 2, Torr P18 i S the partial pressure of mass 18, Torr P2s is the pa rt i a 1 pressure of mass 28, Torr P44 i S the partial pressure of mass 44, Torr Contamination Contamination of the vacuum chamber is to be kept to a m1n1mum. This is of importance so that sparking and breakdown problems can be reduced at the resonator surfaces, feedthroughs and supports. 2.4 Space Limitations The pumping system components are to be either accommodated between the tie rod support structure for the vacuum chamber or located within certain defined regions inside the vacuum chamber itself. 2.5 Compatibility The pumping system components are to be compatible with other cyclo-tron components, i.e. magnet, resonators, beam exit ports, beam probes and stripping foil mechanisms, etc. 2.6 Maintenance Maintenance requirements for the pumping system are to be accommo-dated within the following limitations: - 3 -1) During commissioning it is expected that the vacuum chamber will be opened several times each week. The lid of the chamber can be raised 3 ft to provide access to components inside the chamber. After some time of operation the chamber should not require to be opened more than once every six months. 2) Beam operation will cease for an 8-hour period once a week for routine maintenance; during this time the pressure can be allowed to rise but operating pressure is to be achieved again by the end of the maintenance period. 3) In general, components which require maintenance are to be removable from the vault within ten minutes or located outside the concrete shielding. 2.7 Upset Conditions The pumping system is not to be vulnerable to accidental air inrush or the formation of arcs. 2.8 Radiation Damage . Components which suffer radiation damage are to have lifetimes which satisfy the maintenance criteria. About 80% of the radiation is composed of high energy neutrons and protons and 20% of gamma rays. The radiation levels have approximate values as follows: 1) At the circumference and centre of the machine the levels are 40 and 2.5 Mrad/yr. These estimates are at the 50% confidence level. 2) Diffusion pumps will be located where the maximum radiation levels are about 2 Mrad/yr. Diffusion pump fluid at 4 ft from the median plane will be subject to radiation levels of about 1.5 Mrad/yr. 3) The maximum radiation levels at the circumference and centre of the machine after one hour of cooling are about 12 and 2 rad/h, respectively. The maximum full body dose that a man can tolerate is about 100 mrad/week. 2.9 Instrumentation Remotely controlled vacuum gauges are required to monitor the chamber pressure before and after the beam is in operation. It is preferable but not necessary for the remotely controlled residual gas analyzer to function when the beam is in operation. At about 2 ft from the median plane the magnetic fringing fields in which these instruments are to function have a vertical component of the field of 1500 gauss and transverse field components less than 150 gauss. - 4 -Temperature-sensing devices, liquid level controllers and safety protection devices are all to be remotely controlled and operable in the magnetic fringing fields. 2. 10 Magnetic Shielding Magnetic components, including field distortion shieldin~ are to be avoided where possible. In most cases, if their presence is mandatory, their effect on the cyclotron magnetic field will have to be measured by the TRIUMF magnet group. - 5 -3. RESIDUAL GAS DENSITY AND COMPOSITION A review of the present knowledge of the H- gas stripping cross-section for different gases has been made by Craddock} Specific data are not available for carbon monoxide and water vapour. Thus, the stripping cross-section for these molecules relative to nitrogen is taken to be approximately proportional to the ratio of the number of electrons present. The H- stripping cross-section for hydrogen gas is a factor of ten lower than for nitrogen. The fractional beam current loss/MeV = 2nNcrp/~E where ~E is the energy gain/turn (0.4 MeV), p(cm) is the ion orbit radius at energy E, cr is the cross-section for gas stripping (cm2/atom), and N is gas density (atoms/cm 3). There-fore, 100% hydrogen gas density of 4.6 x 1010 atoms/cm 3 (7 x 10- 7 Torr hydrogen at 22°C) will provide the same beam power loss integrated over energy as a nitrogen gas density of 4.6 x 109 atoms/cm 3 (7 x 10- 8 Torr nitrogen at 22°C). Thus, the specific gas density requirements depend on the percentage composition of the residual gas in the vacuum chamber. This depends on the relative proportions of baked and unbaked surfaces within the chamber, the bakeout time and temperature, and the total pumping time. If the partial pressures of residual gases are p1 , p2 ... Pn and their respective stripping cross-sections for H- ions are cr1 , cr2 , ... cr , then the ratio of beam power loss for this gas composition must bg less than that for 7 x 10-8 Torr of nitrogen: plcrl + p2°2 + ........ p cr < n n 7 X 10-80 (nitrogen) (2) The following values of cr wi 11 be assumed for 500 MeV H- ions: 0(nitrogen) = 3.6 X 10-18 cm2/molecule cr = 3.6 X 10-19 cm2/molecule (hydrogen) cr (carbon = monoxide) 3,6 X 10-18 cm2/molecule cr = 5.8 X 10-18 cm2/molecule (carbon dioxide) cr = 2.2 X 10 -18 cm2/molecule (water vapour) The relationship in criterion 2.2 is obtained from this data. - 6 -4. GAS LOADS AND BAKEOUT Published outgassing rate data for materials vary over two orders of magnitude depending on surface treatment. The data are complex functions of time and pressure and depend critically on the history and clean] iness of the surface. 2 The stainless steel surfaces of the vacuum chamber are to be degreased and glass bead blasted, since this has been experimentally shown to be an effective cleaning treatment, 3- 5 and is quite practical and econom-ical for the TRIUMF chamber. The design values for outgassing rates of baked and unbaked stainless steel and polyurethane are given in Table I. The data for unbaked stainless steel and processed polyurethane at 32°C include safety factors of about 3, and the data for baked stainless steel are esti-mated on the basis of Strausser 1 s 6 published work to have a safety factor of about 10. The resonators,which are to be fabricated from silver-clad aluminum, will be degreased and either mechanically or chemically polished. Literature values vary widely for aluminum and are sparse for silver, but since the resonator surfaces can be more carefully prepared and cleaned than the vacuum chamber, it will be con-servative to use the same outgassing rate data as for stainless steel. Model work has shown that processing polyurethane (Conap Ltd.) by air baking to 80°C for 24 hours followed by a 3-hour air exposure at room temperature reduces the outgassing rate of unprocessed material by a factor of about 5. Such a procedure is recommended, since the gas load from the main seal even after processing forms about 30% of the total mass 18 gas load after 2 hours of pumping. The comparison is made after 2 hours, since this is prior to baking the resonators or other metal surfaces. The effective outgassing surface area of the polyurethane in the groove of the main chamber is taken as 50% of the total geometric surface area of the material. For the gate valve seals the total geometric surface area is used, since the valves are normally open and the mater-ial uncompressed. Permeation through polyurethane is considered for the chamber seal only, and a permeation constant K for air of 0.5 x 10-s cm2/sec is assumed. The hydrogen gas load from loss of beam is 9 x 10-6 Torr 1 it re/sec for 100 µA beam current loss for 200 MeV extracted beam. The high energy neutral hydrogen atoms may yield as many as 10 molecules of adsorbed water vapour per incident atom from the chamber walls. The total gas load Q8 associated with beam loss is therefore about 9.9 x 10-s Torr litre/sec. The overall leak rate specification for space chambers of less than 8 x 10-6 Torr litre/sec will be used for the TRIUMF vacuum chamber and is designated QL, the gas load from real leaks. TABLE l OUTGASSING RATE DESIGN VALUES PUMPING TOTAL MATERIAL TIME COMPONENT OUTGASSING RATE OUTGASSING RATE Torr 1 it re/ h Torr litre/(sec cm2 ) (sec cm2) 2 18 28 44 Unbaked Stainless Steel At 32°C 1 J. 3 X 10- 9 1.5x10- 8 4,0 X 10- 9 4.2 X Jo-lO 2.1 X 10-B At 32°C 2 5. 8 X J o-l O 7,0 X Jo- 9 1.8 X JO- 9 1, 9 X 10-l 0 9,6 X 10- 9 At 32°C 3 4, J X 10- l 0 5,0 X 10- 9 1, 3 X 10- 9 J .4 X 10-lQ 6,9 X 10- 9 At 32°C 12 J, J X J o-l 0 1,3 X JO- 9 3, 3 X 10-l 0 3,6 X 10-ll 1. 7 X 10- 9 At 32°C 15 8,3 X JO- 11 (6) J .Q X JQ- 9 (73) 2.6 X JQ-l0(19) 2.8 X 10- 11 (2) 1.4x10- 9 At 32°C 48 2.5 X 10-ll 3. 1 X Jo-lO 8. 0 X 10-l l 8.4 X 10- 12 4.2 X 10-l0 Baked Stainless Steel '-I At 14O°C 3 2.8 X 10- 8 (10) 1.3 X JQ- 7 (53) 8.8 X 10- 8 (35) 3, 7 X 10- 9 (2) 2.5 X 10- 7 At 14O°C 12 J ,5 X 10- 8 (23) 2.9 X JO- 8 (45) 2.0 X 10- 8 (31) 6. 5 X 10- l O ( J ) 6.5 X 10- 8 At 32°C 15 7,8 X 10-ll(79) 2.0 X JO- 11 (21) 1 ,Q X 10-l0 At 32°C 48 7, 8 X 10- ll ( 79) 2.0 X 10-ll(2J) J ,Q X 10-l0 Processed Polturethane At 32°C 1 5,6 X 10- 7 2. J X 10-S J . 2 X J o- 6 2.3 X 10-S At 32°C 2 4.J X JQ- 7 J,5 X JQ-S 9.0 X JQ- 7 1.6 X 10-S At 32°C 3 3,3 X 10- 7 1 .2 X Jo-S 7,2 X 10- 7 1.3 X 10-S At 32°C 12 1.7 X J0- 7 6.3 X 10- 6 3, 7 X 10- 7 6,7 X 10- 6 At 32°C 15 J,5 X JQ- 7 (2,5) 5,4 X 10- 6 (92) 3,2 X JQ- 7 (5.5) 5.8 X 10- 6 At 32°C 48 8.5 X JQ- 8 3, J X 10- 6 1 ,9 X 10- 7 3.4 X 10- 6 Percentage composition values are stated in brackets. - 8 -The gas load from mechanisms inside the vacuum chamber,~• is unknown, since the design of these components is not detailed. It is reasonable to assume that the mechanisms can be effectively cleaned and will be mainly metal or some other material compatible with ultra-high vacuum. Therefore, a gas load assumed to be equal to Q5 , the gas load from the unbaked chamber, will be used to allow for loads from this source. The legend for the sources of gas load are provided in Figure I, and the total and component gas loads are plotted as a function of time in Figure 2. Table I I summarizes the total and component gas loads for half the chamber after 15 hours of pumping. The data for an unbaked vacuum chamber, processed chamber seal and resonators baked to 140°C have been used for this table, since these operating conditions have been shown to be both practical and necessary in order to satisfy criteria 2. l and 2.2 for the cryopumping system described in Section 10. The residual gas pressure analysis after 15 hours of pumping for the cryopumping system, Table I I I, shows that using the design gas loads criterion 2.2 is only just satisfied. Table IV shows that some bakeout of the vacuum chamber is required to satisfy criterion 2.2 for the 32 in. oil diffusion pumping system when a processed chamber seal is used and the resonators have been baked to 140°C. This is also true even for a metal main chamber seal. The factor which primarily determines the chamber bakeout requirement is the space limitation, which dictates the maximum number of diffusion pumps that can be used and therefore the maximum mass 28 pumping speed available on the system. Experimental values of outgassing rates of stainless steel after bakeout to temperatures less than 140°C are not available at the present time. Since the maximum reliable baking temperature of the polyurethane vacuum chamber seal is also not known, it is not feasible to quantitatively predict the chamber pumpdown performance for a baked chamber and baked resonators condition. However, if the resonators are baked to l40°C and the vacuum chamber and seal mildly baked, it should certainly be possible to reduce the gas load sufficiently to satisfy criteria 2.2 and 2. l using the 32 in. oil diffusion pumping system. The specific combination of baking time and temperature, warm-up and cool-down time of the vacuum chamber, etc. which are required is determined by the maximum baking tempera-ture that the polyurethane seal can withstand. The mandatory require-ment to bake the chamber and seal is a significant disadvantage of the oil diffusion pumping system compared to the cryopumping system. Since criteria 2.2 and 2. l are only just satisfied for the cryopumping system using the design gas loads, the chamber bakeout function is advisable as an additional safety factor and for use to clean up the chamber in the case of a water leak. When radiation levels are low, viton can be used to replace polyurethane if seal failures occur when baking. TABLE I I GAS LOAD AFTER PUMPING TIME OF 15 HOURS - (HALF CHAMBER) SOURCE AREA OUTGASSING TOTAL COMPONENT OF GAS RATE GAS LOAD GAS LOAD (Legend of Q cm2 Torr' litre/ Torr litre/sec Torr litre/sec (sec cm2 ) in Figure 1) 2 18 28 44 Qo (32°c) 2 .0 X 106 1.0 X 10-lO 2.0 X 10- 4 1.6 X 10- 4 4.2 X 10-S Qd (32°c) 3.3 X 106 1.0 X 10-lO 3.3 X 10- 4 2.6 X 10- 4 6.9 X 10-S Qs (32°c) 1.2 x 106 1.4 X 10- 9 ] .6 X 10- 3 9.6 X 10-S ].2 X 10- 3 3.] X 1 o-4 3.2 X 10-S Q (32°c) 1. 0 X ] 06 1.4 X 10- 9 1.4xl0- 3 8.lxl0- 5 9.8 X 10- 4 2.6 X 10- 4 2.7 X 10-S 6,9 2.3 X 106 1.0xJO-lO 2.3 X 10- 4 ].8 X 10- 4 4.8 X 10-S Q1,s (320c) \.0 Qs (32°c) 2.6 X ]03 5. 8 X 10- 6 1.5 X 10- 2 3.8 X 10- 4 1. 4 X 10- 2 8.3 X 10- 4 Q' (32°c) 3.0 X 102 5. 8 X 10- 6 l.7xl0- 3 4.4 X 10-S J.6 X 10- 3 9.6 X 10-S s Qp ] .2 X ]03 5.3 X 10- 6 3.0 X 10- 7 5.0 X 10- 6 QB 5.0 X 10-S 4.5 X ]Q-6 4.5 X 10-S QL 4.0 X 10-6 2.0 X 10- 7 3.8 X 10- 6 QM (32°c) ] . 2 X ) 06 1.4x10- 9 1.6xl0- 3 9.6 X 10-S ] . 2 X 10- 3 3.] X 10- 4 J.2 X 10-S ¾ 2.] X 10- 2 8.8 X 10- 4 1. 9 X 10- 2 ] .8 X 10- 3 9.lx10-5 QT= Qo + Qd + ¾ 2.2 X 10- 2 1.3 X 10- 3 1.9 X 10- 2 ] . 9 X 10- 3 9. 1 X 10-S TABLE I I I PRESSURE CALCULATION SUMMARY AFTER PUMPING TIME OF 15 HOURS FOR CRYOPUMPING SYSTEM SOURCE AREA OUTGASSING TOTAL TOTAL TOTAL SCS OF GAS RATE GAS LOAD MASS NUMBER PRESSURE PRESSURE Torr litre/ Torr 1 i tre/ cm2 (sec cm2) sec Torr Torr .. 2 18 28 44 Qo 2.0 X 106 1.0 X 10-l0 • 2.0 X 10- 4 1.6 X 10- 4 4.2 X JO-S Qd 3.3 X 106 1.0 X 10-l0 3.3 X 10- 4 2.6 X 10- 4 6.9 X 10-S Q6,9 1. 0 x l 06 1 .4 X 10- 9 1 .4 X 10- 3 8.] X 10-S 9.8 X 10- 4 2.6 X 10- 4 2,7 X 10-s Q7 8 2.3 X 106 1.0 X 10-l0 2,3 X 10- 4 l.8x10- 4 4.8 X 10-S ' ¾ 2 .1 X 10- 2 8.8 X 10- 4 1 .9 X 10- 2 1 .8 X 10- 3 9. 1 X lQ-S QT 2.2 X 10-2 1.4xlo- 3 1 .9° X 10- 2 2.0 X 10- 3 9. 1 X 1 o-S I s 12,800 840,000 74,500 59,500 -0 1. 1 X 10- 7 2.3 X 10- 8 2.7 X 10- 8 1.6xl0- 9 1 .6 X 10- 7 I pl op 1 .1 X 10- 8 1.4 X 10- 8 2.7 X 10- 8 2.6 X 10- 9 5,5 X 10- 8 1 1 3,0 X 105 1 ,4 X 10- 9 4.0 X 10- 4 2.4 X 10-S 2.9 X 10- 4 7,5 X 10-S 8.0 X 10- 6 2 ql2Hl2Ll2 Ql2 2.5 X 10-3 7,1 X 10- 4 1.3 X 10- 3 4.9 X 10- 4 3.5 X 1O-S Cl2 875,000 293,000 235,000 188,000 P2-P1 8,0 X lQ-l0 4.3 X 10- 9 2.lxl0- 9 1.9 X 10-10 7,4 X 10- 9 5.9 X 10- 9 1 2 q23H2l23 4,9 X 105 1.ox10- 10 4.9 X 1O-S 3.9x 10-5 1 .0 X JO-S Q23 2.5 X 10-4 2.0 X 10- 4 5.2 X 10-S C 74,000 25,000 19,900 12,000 23 p3-p2 2.6 X 1O-l0 2.6 X 10-9 2.9 X 10-g 2,6 X 10- 9 P3 1. l x 10-7 2,7 X 10- 8 3,2 X 10-S 1.8 X 10- 9 1. 7 X 10- 7 OP3 1.1 X ]Q-S 1.6 X 1O-S 3,2 X 10-S 2:9 X 10-9 6.4 X 10-S TABLE IV PRESSURE CALCULATION SUMMARY AFTER PUMPING TIME OF 15 HOURS FOR DIFFUSION PUMPING SYSTEM SOURCE OUTGASSING TOTAL TOTAL TOTAL SCS OF GAS AREA RATE GAS LOAD MASS NUMBER PRESSURE PRESSURE Torr litre/ Torr litre/ Torr Torr cm2 (sec cm2) sec 2 18 28 44 Qo 2.Q X 106 1.0 X 10-lo 2.0 X 10- 4 1.6 X 10- 4 4.2 X 10- 5 Qd 3.3 X 106 1.ox10- 10 3.3 X 10- 4 2 .6 X 10- 4 6.9 X 10- 5 Q6 .9 1. 0 X 106 1.4 X 10- 9 1.4 X 10- 3 8. 1 X 10- 5 9.8 X 10- 4 2.6 X 10- 4 2.7x 10- 5 ' Q7 8 2.3 X 106 1.ox10- 10 2.3 X 10- 4 1. 8 X 10- 4 4.8 X 10- 5 ' ¾ 2.lxl0- 2 8.8 X 10- 4 1,9 X 10- 2 l.8x10- 3 9.1 X 10- 5 QT 2.2 X 10- 2 1.4xl0- 3 1.9x10- 2 2.0 X 10- 3 9.1x10- 5 I s 66,900 114,000 26,700 72,000 --P1 2.lxl0-8 l.6x10- 7 7.5 X 10- 8 1.3 X 10- 9 2 ,5 X 10- 7 I crpl 2. 1 X 10- 9 1.0 X 10- 7 7.5 X 10- 8 2.0 X 10- 9 1. 8 X 10- 7 1 3.0 X 10;5 1.4x10- 9 4.0 X 10- 4 2. 4 X 10- 5 2.9 X 10- 4 7.5 X 10- 5 8.0 X 10- 6 - q H L 2 12 12 12 Ql2 2.5 X 10-3 7. 1 X 10- 4 1.3 X 10- 3 4.9 X 10- 4 3.5 X 10- 5 Cl2 875,000 293,000 235,000 188,000 p2-pl 8.0 X 10-l0 4.3 X 10- 9 2.lxl0- 9 1.9 X 10-lO 7 .4 X 10- 9 5.9 X 10- 9 1 4.9 X 105 1. 0 X 10-l 0 4,9 X 10- 5 3,9 X 10- 5 1.0 X 10- 5 2 q23H2l23 Q23 2.5 X 10-4 2.0 X 10- 4 5.2 X 10- 5 C23 74,000 25,000 19,900 12,000 P3-P2 2.6 X 10-l0 2.6 X 10- 9 5.2 X 10- 9 2.9 X 10-9 P3 2.2 X 10-8 1. 6 X 10- 7 8.0 X 10- 8 1 ,5 X 10- 9 2.6 X 10- 7 crp3 2.2 X 10- 9 1 .0 X 10- 7 8.0 X 10- 8 2.2 X lQ- 9 1.9 X 10- 7 - 12 -The factors which determine the requirement for baking the resonators for either the cryopumping system or the 32 in. oil diffusion pumping system are the surface area and operating temperature of the resonators, the pumpdown time criterion 2. 1, and the conductance of the duct provided by the beam aperture, i.e. the space vertically restricted by the hot arms of the top and bottom resonators. The mass 18 gas load from the polyurethane seal can be adequately handled by the cryopumping system and is not a serious limit for this system. For the baking schedule of the resonators theassumption has been made that one hour is required to reach operating temperature and three hours are required for the resonators and vacuum chamber to cool from 140°C to 32°C. Tables I I I and IV indicate the importance of correct analysis of the residual gas composition, particularly for the cryopumping system, since although the stripping cross-section value of p3 in Table I I I of 6.4 x 10-B Torr meets criterion 2.2, the total gas pressure is only 1.7 x 10- 7 Torr. Table V is a summary of a pressure analysis for the cryopumping and diffusion pumping systems, for the cases of baked and unbaked resonators, different main chamber seal materials and different pumping times. TABLE V PRESSURE ANALYSIS UMMARY PUMPING PUMPING CHAMBER RESONATOR SEAL SYSTEM TIME CONDITION CONDITION MAT. P1 (SCS) P2 (SCS) P3 (SCS) COMMENTS h Torr Torr Torr Cryopump ( 15) Unbaked Baked Poly. 5.5 X 10-8 6. 1 X 1 o- 8 6.4 X J0- 8 Cryopump ( 15) Unbaked Baked Metal 3.3 X J0- 8 3.9 X 10- 9 4.2 xl 10- 8 Cryopump ( 15) Unbaked Unbaked Poly. 8.3 X J0- 8 1. 1 X 10-7 2 .1 X 10-7 R need baking Cryopump ( 15) Unbaked Unbaked Metal 7.0 X J0- 8 1 .0 X 1 o- 7 2.0 X J0- 7 R need baking Cryopump (48) Unbaked Baked Poly. 2.6 X 10-8 2.8 X J0- 8 3.1 X J0- 8 Cryopump (48) Unbaked Unbaked Poly. 3.8 X J0- 8 4.7 X 10- 8 7,] X J0- 8 R need baking w Diffusion ( 15) Unbaked Baked Poly. 1.8 X J0- 7 1.9xlo- 7 1 .9 X 10-7 C needs baking Diffusion ( 15) Unbaked Baked Metal 9,9 X 10- 8 1. 1 X 10- 7 1. 1 X 10-7 C needs baking Diffusion ( 15) Unbaked Unbaked Poly. 4.0 X 10-7 4,3 X J0- 7 5.3 X JQ-7 R & C need baking Diffusion ( 15) Unbaked Unbaked Metal 2.6 X 10- 7 2.9 X J0- 7 3.9 X JQ-7 R & C need baking Diffusion (48) Unbaked Baked Poly. 1.2 X J0- 7 1.2xlo- 7 1.3 X 10- 7 C needs baking Diffusion ( 15) Unbaked Baked Poly. 1. 1 X 10-7 1.1 X 10-7 1. 2 X 1 o- 7 C needs baking + 750,000 1 i tre/sec for mass 18 Diffusion ( 15) Baked Baked Poly. <].Ox 10-8 See Section 4 - 14 -5, CONDUCTANCE OF VACUUM CHAMBER AND RESONATORS The gas density varies in a complicated way as a function of radius; maximum values are formed along the centre line between each half of the resonator structure, since pumps must be symmetrically located with respect to the resonators on each half of the chamber. It is conservative and convenient to apply the operating pressure criterion 2.2 to this centre line. The following equations apply 7 where p , p and p are at the positions shown in Figure 1: 1 2 3 (3) (4) (5) The conductances C12, C23 for mass 2, 18, 28 and 44 and the values of H12L12/2 and H23L23/2 are shown in Table VI: TABLE VI CONSTANTS FOR EQUATIONS (3), (4), AND (5) CONDUCTANCE MASS NUMBER 1 it re/sec 2 18 28 44 Cl2 875,000 293,000 235,000 188,000 C 74,000 25,000 19,900 12,000 23 Hl2Ll2 3.0 x 105cm2 , H23L23 4.9 x 105cm2 2 = 2 = The pressure gradients (p2-p 1) and (p3-p 2) depend only on the gas loads and conductances of the resonator and vacuum chamber surfaces. Holes in the back end of the resonators would eliminate~ from equation (5) and reduce the magnitude of (p3-p 2 ) but would not remove the necessity for reducing the total gas load tram the resonators by baking. The baking temperature and time required depend on the conductance of the duct c23 and the degree to which assumed outgas-sing rates of the resonators are realistic. - 15 -6. PUMPING SPEEDS Pumping speed requirements to satisfy criteria 2. 1 and 2.2 depend on the magnitude of the gas load. This may be reduced by selecting appropriate methods of chamber fabrication and surface preparation. The gas load is also affected by the mode of chamber operation. The optimum pumping system cannot be selected until these factors have been established. For the 32 in. liquid nitrogen trapped oil diffusion pumping system, the maximum number of pumping stacks that can be conveniently attached to the TRIUMF vacuum chamber is only six units, and therefore the maximum available pumping speeds for mass 2, 18, 28 and 44 are limited by space restrictions. Economics rather than space limitations determine the cryopump surface area and hence available pumping speeds for mass 28 and 18. For the cryopumping system it is desirable to minimize the required pumping speed for mass 2 from 10 in. oil diffusion pumps by allowing the partial pressure of hydrogen to reach a maximum level compatible with the economics of the pumping speeds for mass 18, 28 and 44 from the cryopump. It should thus be possible to reduce the probability of oil contamination reaching the vacuum chamber to an extremely low level. Sections 9 and 10 will detail the magnitude of the component gas pump-ing speeds for the diffusion pumping system and cryopumping system, respectively. - 16 -7. SURVEY OF VARIOUS TYPES OF PUMPS Each pump type is assessed in relation to its application to the TRIUMF vacuum chamber, both as a primary and as an auxiliary pumping method. The economics of each method are not considered in detail, since this depends on the total system concept, which must include the cost of the roughing and auxiliary pumping system and necessary vacuum chamber and building modifications. The pump types considered below are only those which have been rejected for further considera-tion for pumping the main TRIUMF chamber. 7. l Turbomolecular Pump For pumping the chamber withturbomolecular pumps, two approaches can be considered: l) Six Pfeiffer 15000 TVP pumps (4100 litres/sec) mounted above the overhead support structure, as a primary pumping method. 2) About six Welch 3102 pumps (260 litreshec) placed beneath the vacuum chamber, as an auxiliary pumping method, i.e. in combination with cryopumping or titanium sublimation pumping. The exact number of pumps required depends on the primary pumping system chosen. Advantages l) The pump is capable of operating for an unlimited time on any part of its throughput range. 2) Users report that the pump is highly reliable. Maintenance time is only 25% of that spent on maintaining oil diffusion pumps. 3) Correct pump operation can eliminate the need for liquid nitrogen traps. 4) Fast-closing valves are not required in the case of a catas-trophic air leak in the chamber or a power failure. 5) Auxiliary pumps for resonator bakeout are not required. Disadvantages l) Pfeiffer have made calculations and experimental measurements of the maximum magnetic fringing field normal to the rotor which the pump can withstand before expansion of the rotor by eddy current heating becomes a problem. A maximum tolerable expansion equal to half the clearance between the rotor and stator is obtained with a magnetic field of about 100 gauss. - 17 -2) A 26 ft 3 mild steel shield for the Pfeiffer pump placed 9 ft above the median plane at a radius of 250 in. changes certain regions of the cyclotron magnetic field by 7 gauss. The shielding would need to be symmetrically placed in all six valleys to overcome harmonic problems and the trim coil capacity sufficient to correct for the field perturbations. 3) Magnetic shielding problems and space limitations dictate that the Pfeiffer pump must be located about 9 ft from the chamber wall above the tie rod array and connected to the chamber by 18 in. diameter vertical tubes. Provision must be made in the building design for removal of each pump for servicing once each year. The Welch pump must also be connected to the chamber using tubes of similar diameter and length so that magnetic shield-ing problems can be minimized. 4) Space restrictions and economics limit the number of Pfeiffer pumps that can be used. Therefore, either significant reduction of the total gas load by baking is required to meet criteria 2. 1 and 2.2 or an additional high speed method of pumping is needed during the first few days of pumping. 5) Reports have been published of turbine oil which lubricates the bearings reaching the vacuum chamber when the pump is turned off. Correct pump operation can minimize oil migra-tion; otherwise liquid nitrogen traps are required with the pump. 6) The pumping speed to cost ratio is low compared to most other pumping methods. The pump has some attractive features as an auxiliary pumping method only. Since the liquid nitrogen trapped oil diffusion pump has no operational difficulties in a magnetic field, the latter pump must be considered as being more suitable for TRIUMF than the turbomolecular pump. 7,2 Titanium Sublimation Pump Titanium can be sublimed from a source onto liquid nitrogen cooled walls of a separate chamber, which is flange mounted onto the cyclotron vacuum chamber. Since the pumping speed to cost ratio is high for such a system, it will be considered as a primary pumping method. An auxiliary pumping method is required to remove non-getterable gases such as methane, helium and argon from the chamber during resonator bakeout and for leak testing. Advantages 1) The method is free from hydrocarbon contamination. - 18 -2) The pump is fail-safe in the case of power failure. 3) The pumping speed to cost ratio is high; valves are not required. 4) The pumps can be oriented in any required direction. Disadvantages 1) Maximum magnetic fringing fields that an electron-bombarded titanium slug can tolerate are about 50 gauss. A 1 ft 3 mild steel shield placed 30 in. from the median plane at a radius of 130 in. changes certain regions of the cyclotron magnetic field by 18 gauss. The trim coil capacity would need to be sufficient to correct for field perturbation~ as for turbomolecular pumps. There are likely to be some problems shielding the subl imator which is located inside a large diameter sublimation pump chamber. 2) The magnitude of the gas load after baking the resonators and 15 hours of pumping is such that a total continuous sublimation rate greater than 0. 15 g/hour is required to pump mass 2, 28 and 44. Resistance-heated and electron-bombarded sublimators have maximum capacities of 30 g and 200 g, respectively. The recommended sublimation rate from one source is about 0.03 g/hour. Therefore, a minimum of about six shielded electron-bombarded sublimators or 18 resistance-heated sublimators is required for six months continuous operation. 3) Maintenance requirements due to filament failure can be serious, particularly if there is a leak in the vacuum chamber. Vacuum lock devices for the subl imator would be needed. 4) The sublimation pump walls must be cleaned periodically when the film becomes too thick and starts to overheat or peel. The pump must be removed completely from the vault for this procedure. S) Titanium can be a significant gas source if it is not thoroughly outgassed prior to sublimation and if the subli-mated film becomes heated by radiation from the sublimator. Although maintenance and magnetic shielding requirements are the major disadvantages of titanium pumping for TRIUMF when considered as a primary pumping method, its use as an auxiliary pump to the 20°K cryopumping system has some attractive features. It can be used as an excellent pump for hydrogen during normal cyclotron operation, in place of oil diffusion pumps. However, the 1 iquid nitrogen trapped oil diffusion pumps are still required during resonator bakeout and cryopump defrosting. Since these periods of time are a small fraction of the total operating - 19 -time, the probability of oil reaching the vacuum chamber is reduced to a negligible level. It is feasible to attach two titanium pumps, on each half of the chamber, below the 12 in. i .d. throttle-isolation valves, and thereby provide sufficient pumping speed for hydrogen for six months. Although helium cannot be removed by the cryopump or titanium pump, the diffu-sion pumps can be operated during weekly maintenance periods to reduce the helium concentration if it becomes too high. ].3 Sputter-Ion Pump The sputter-ion pump can be used as an auxiliary pumping method in two ways. Either custom-designed arrays of sputter ion cells can be placed inside the vacuum chamber to utilize the uniform field of the cyclotron magnet, or standard sputter-ion pumps can be attached to the chamber by high conductance tubes. Advantages 1) The pump is fail-safe in the case of power failure. 2) The custom-designed arrays utilize space which cannot be used by pumping methods other than cryopumping; valves are not required. 3) The pump is reliable and requires serv1c1ng at intervals (6-month) when operated in the 10- 7 Torr range. Disadvantages 1) The pumping speed to cost ratio is low for both the custom-designed and standard ion pumps. 2) An angular deviation of the resultant magnetic field vector of 2° causes a 10% decrease in pumping speed of an 8 litre/ sec sputter-ion pump. It is necessary to orient the magnetic field of the ion pump parallel to the direction of the resultant magnetic field at any position. Even if this were done, it would not be possible to guarantee the pump performance, since sections of the pump cell array would be located in different magnetic field geometries. Shielding for ion pumps would affect trimming coil capacities as previously described for the turbomolecular pump. 3) Maintenance is a severe problem for cell arrays located in-side the vacuum chamber. 4) The adsorption capacity of sputter-ion cells for hydrogen is limited. Periodic maintenance for cell replacement is necessary. - 20 -5) Rough pumping to below 10- 4 Torr is required for standard ion pumps so that heating instability problems during high throughput periods can be minimized. Rough pumping to 10-s Torr is desirable for the cell arrays inside the vacuum chamber, so that the size of current-carrying conductors and the number of power supplies can be minimized. 6) An additional pumping system is required for the cell array when the magnetic field is turned off, and for both the cell array and standard pump during resonator bakeout and for leak testing. 7.4 Cryosorption Pump The cryosorption pump can operate as a primary pump during cyclo-tron operation and requires auxiliary pumping only during resonator bakeout, initial leak testing of the chamber, and reactivation of the molecular sieve adsorbent. Advantages 1) The method is free from hydrocarbon contamination. 2) The pumping speed to cost ratio is high for high pumping speed requirements. 3) The pump has a significant capacity for hydrogen in the tem-perature range 4.2°K to 20°K. 4) The pumping speed for a particular gas is independent of chamber pressure until 25% of the isotherm capacity of the molecular sieve has been pumped. The thickness of the absorbent bed is a relevant factor. 5) The pump is completely unaffected by cyclotron magnetic fringing fields. 6) The pump can be oriented in any required direction. Disadvantages 1) There is very little operational experience with commercial-ly available cryosorption panels for pumping relatively large gas loads for long time periods in the high 10- 8 Torr range. 2) Periodic activation at 200°C of the molecular sieve is required to restore its capacity to adsorb gas. The contin-uous running time between activations depends on sieve temperature. Calculations indicate that it is of the order of 3 to 4 months at l x 10- 7 Torr of hydrogen. - 21 -3) Cracking or dusting of molecular sieve is a potential problem although some users report that dusting has not been observed after 20 activations at 250°C. 4) Rough pumping of the chamber to below 10- 4 Torr is required. 5) The properties of radioactive molecular sieve are unknown. 7-5 Cryopumps Operating at or below 4.2°K A cryopump at 4.2°K and below can operate as a pri~ary pump during cyclotron operation and requires auxiliary pumping only during resonator bakeout, leak testing of the chamber, and defrosting the cryopump surfaces. Advantages 1) The method is free from hydrocarbon contamination. 2) At 2.5°K the pump has a high sticking coefficient (0.95) for hydrogen and the ability to pump large quantities of hydrogen without loss of pumping performance at background gas densities equivalent to l x 10-7 Torr. 3) The pump can be oriented in any required direction. Disadvantages l) The costs of operation at 4.2°K are about five times greater than at 20°K. 2) At 4.2°K the cryopump can pump hydrogen for only a few days before the hydrogen must be removed by warming the surface to 20°K, so that the pumping speed of hydrogen at 4.2°K can be re-established. 3) It is unfortunate that there is relatively little or no experience with cryopumping below 4.2°K, for time periods longer than a few days, and operational procedures are likely to be difficult. This is not a disadvantage inherent in the method of pumping, however. - 22 -8. ROUGHING SYSTEM The roughing system should be capable of reducing the chamber pressure from atmospheric to approximately 2 x 10-2 Torr in about two hours. It must have adequate pumping speed for leak testing and will act as a back-up for the diffusion pump backing system. Since the roughing system during normal operation will only be run for two hours approximately four times a year, the equipment will not accumulate many operating hours. However, the system must be capable of starting at any time in case of backing system failure, and for scheduled and unscheduled pumpdowns. Roots-type blowers develop high pumping speeds in the 20-micron region but require backing pumps to bring pressures below 25 Torr where the blowers can be run continuously. Blowers of the Roots type have been used for vacuum pumping applications for approximately ten years, and reliable units have been developed which are used in various industrial applications, for instance, in the vacuum degassing of steel on a production basis. The proposed system is shown in Figure 3. The system will be purchased as a complete integrated unit. The roughing system required for use with 32 in. diffusion pumps is slightly different from that used with the cryosystem because of the necessity of allowing the blowers to be used as stand-by for the much larger backing system of the diffusion pumps. 8. 1 Description of Pumping Components 8. 1. 1 Roughing Pumps The roughing system will consist of two 500 cfm blowers in parallel, each backed by a 150 cfm rotary oil seal pump. 8. 1.2 Roughing Line Trap The 12 in. diam roughing line will have a liquid nitrogen cooled trap and an isolation valve at the entrance to the chamber. Blowers will be protected by an impinging-type trap for large particles and oil, and a mesh screen for small particles. Exhausting of rotary pump oil will be controlled by an oil trap on the exhaust of each pump. Migration of oil from the rotary pumps may be controlled by a molecular sieve trap, or alternatively by a liquid nitrogen trap. 8. 1.3 Roughing System Valves Isolation valves will be of the gate type and air operated. The valving system will be such that any pump unit can be removed for servicing while the system remains in service .(at lower capacity). Rotary pump forelines will be vented to atmosphere in case of pump shutdown by means of automatic vent valves, which at the same time isolate the vacuum chamber. - 23 -The isolation valve at the chamber entrance is identical to those used in the auxiliary diffusion pump system. 8.1 .4 Roughing Line The roughingline is 12 in. diam and is stainless steel through-out. Stainless steel is necessary in the vicinity of the cyclotron to minimize interaction with the magnetic fields, and is preferable elsewhere to prevent formation of rust and scale, which would interfere with pump operation. 8.1 .5 Roughing System Exhaust The roughing system exhaust will be fed into the air disposal system. 8. 1.6 Building Requirements No. Reqd. 1 1 2 Overall dimensions, weights, power and water consumption, and location of the pumping components are listed in Table Vil. TABLE VII BUILDING REQUIREMENTS OF ROUGHING SYSTEM Size Weight Power Water Equipment Location each each each each ] 2 II valve l 280 1 b - -Vacuum See 12'' trap Chamber Fig.37 250 1 b - -Pumping units, consisting of one 500 cfm Mechanical 5011 H X blower, one Services 4911 X 1685 1 b 8 hp 1. 5 gpm 150 cfm rotary Room 3111 pump and asso-ciated valves - 24 -8.2 Instrumentation and Controls The roughing system will be controlled remotely from the main control panel during normal operation and from the vacuum control panel during start-up of the pumps, leak testing and maintenance. The roughing system pumping units consisting of blower, backing pump and valves will essentially be supplied as self-contained units complete with internal controls, such as pressure switches to start the blowers and automatic vent valves which seal the system and vent the rotary pump foreline in case of power failure. However, system status information will be fed back to the control panels at all times. 8.3 Maintenance Requirements Regular maintenance will include changing lubricating oil in the machine gearboxes every 1000 hours and changing shaft seals at 5000-hour intervals. Pumps of the 11canned motor 11 variety have a definite advantage over the normal type from the point of view of maintenance because of the absence of shaft seals. This type of pump, manufactured by Heraeus, also has the distinct advantage of a motor directly connected to the pump, eliminating maintenance associated with V-belt drives. Major maintenance will be done by returning the unit to the supplier, but this should not be required in the expected 1 ifetime of the cyclotron, since equipment of this type has a mean time between failures of approximately 30,000 hours, and the roughing system is used only occasionally. 8.4 Test Requirements After equipment installation, the following testing procedure will be used: l) Check mechanical operation 2) Check control functions 3) Test for performance (i.e., measure blank-off pressure) 4) Leak test the system 8.5 Operation and Performance Prior to roughing system start-up, all valves will be in the open position except the automatic vent valve and interconnect valves between the roughing and backing system. Rotary pumps are then started and when base pressure has been reached, the automatic - 25 -vent valves are opened. After approximately 45 minutes a line pressure of 20 Torr will have been reached and the blowers are started. (Blowers have been windmilling up to this point.) Diffusion pump cut-in pressure of 2 x 10-2 Torr is reached in about 75 minutes, and when the chamber pressure reaches 1 x 10- 3 Torr the roughing system is isolated from the vacuum chamber and is shut down. Chamber pumpdown performance is shown in Figures 4 and 5. 8.6 Cost Estimates The estimated capital cost and annual operating costs of the roughing system are shown below: Capital Cost: 1211 diam isolation valve 1211 diam cold trap Pumping units (blower and rotary) Valves and traps Mi see 11 aneous Installation and testing TOTAL Annual Operating Costs: Technician Maintenance Consumables and miscellaneous TOTAL Cr:z:os:z:stem $ 2,820 3,320 10,250 4,980 7,710 2,220 $31,300 $ 320 600 100 $1,020 D.P. System $ 2,820 3,320 10,250 5,780 8,040 2,320 $32,530 - 26 -9. 32 IN. DIFFUSION PUMP SYSTEM Diffusion pumps have been widely used to obtain pressures in the 10- 7 Torr range. Total pumping speed available is limited by the size and number of diffusion pumps, which in turn are limited by the physical space available in the TRIUMF machine. Six 32 in. (nominal) diffusion pumps are the practical maximum; a schematic diagram of the 32 in. diffusion pump system is shown in Figure 7, 9. l Description of Stack Components The cyclotron magnetic field and the sensitivity of the beam to ex-ternal magnetic fields preclude the use of magnetic materials in the pumping stacks. The high radiation levels dictate the use of metallic seals throughout the stack, except for the gate seal of the valve, which will be an elastomer. 9.1.1 Diffusion Pumps The radiation environment in which the diffusion pumps are situated favours the use of polyphenol ether as pump fluid and metal-sealed dipsticks as fluid level indicators. To reduce oil backstreaming during normal operation, the top jet of the diffusion pump will be equipped with a cold cap device. To reduce the magnitude of massive oil backstreaming in case of system upset, diffusion pump boilers will be equipped with quick-cooling coils. Boiler heaters will be easily replaceable without requiring dismantling of stack. 9, 1.2 Diffusion Pump Traps Diffusion pump traps will be of the double-bounce variety with water baffles and liquid nitrogen baffles in combination. The liquid nitrogen baffle will be of the reservoir type. 9.1.3 Isolation Valves Isolation valves will be air operated and must be capable of throttling as well as quick closing in case of system upset. Commercially available valves have a closing time of about 10 seconds. Because of the severe radiation environment, valves must use metallic seals throughout, except on the main gate seal where the use of an elastomer is permissible. This requirement also applies to seals in the actuator, i.e. piston sealing 0-rings, etc. The gate seal is replaced by removing the valve mechanism, replacing the gate seal and replacing the valve mechanism. The valve body remains in place during this operation. 9. 1.4 Backing System The large throughput capabilities of the 32 in. diffusion pumps demand a backing system consisting of a combination of - 27 -800 cfm blowers and 150 cfm rotary pumps, as shown in Figure 8. The large capacity of the blowers is required to provide the necessary gas handling capacity during pumping and baking. These units would be purchased as a package, similar to the roughing system. The backing system is connected to the roughing system in such a way as to allow the use of either half of the roughing system in case of backing system failure. The foreline will be 10 in. diam stainless steel pipe. 9.1.5 Refrigeration for Diffusion Pump Cold Traps A supply of refrigeration at 80°K is required for the opera-tion of cold traps in the diffusion pump stacks and the roughing line. Each cold trap requires about 220 watts of refrigeration at 80°K. The total load at 80°K, including transfer lines, is about 2200 watts. This requirement could be fulfilled by a closed loop, sub-cooled liquid nitrogen system, with or without a nitrogen liquefier. The requirement may also be satisfied by a simple open circuit, low pressure liquid nitrogen supply. Both possibilities have been evaluated, and the open circuit system selected. The major differences between the two systems are: 1) A significant thermal load is introduced by the circulat-ing pump required by the closed circuit system. 2) The higher nitrogen consumption of the open circuit system will justify the supply of the liquid nitrogen tank by the supplier of liquid nitrogen. The selected system is shown schematically in Figure 9, Liquid nitrogen from a comme re i a 1 supp 1 y is stored in a tank of not less than 2000 US gallon capacity. Under steady-state condi-tions liquid nitrogen consumption is about 13 US gal/hour. For cooldown each 32 in. trap requires about 25 US gal of liquid nitrogen and the transfer line about 40 US gal of liquid nitrogen. The storage tank is maintained at 20 psig by vapourizing liquid in an ambient air heat exchanger. Liquid nitrogen flows through a standard semiflex transfer line to a point near the vault where a bayonet connection is made with a semiflex transfer line suitable for the radiation environ-ment. Each cold trap is equipped with a remotely operated valve to control liquid nitrogen flow and a manual valve so that any one trap may be removed. Liquid nitrogen flow will be initiated by a timer and terminated by a 1 iquid sensor on the outlet side of each trap. The timer will also over-ride the liquid sensor in the event of sensor failure. Nitrogen - 28 -vapour is returned from. the vault by a run of ·copper tubing and discharged to the vault ventilation system. Capital cost of the system has been estimated at $43,400 and operating costs at $28,800 per year (amortization not - included), with liquid nitrogen at 6¢ per litre, out of the supplier's tank. A comparative analysis was made of a sub-cooled closed-circuit liquid nitrogen system utilizing a Philips PPG-4OO machine as a nitrogen recondenser. Capital and operating costs of this system are compared with the open liquid nitrogen system in Table VIII. TABLE V 111 ECONOMIC OMPARISON OF 8O°K SYSTEMS FOR 32" COLD TRAPS Closed Open LN2 Sub-cooled System LN2 System Capital cost $43,000 $96,900 Direct operating cost/yr 28,800 20,600 Amortization (1O-year straight line) 4,300 9,700 Total cost/yr $33,100 $30,300 The simplicity, and thus inherent reliability, of the open liquid nitrogen system makes this concept desirable for about equal operating costs. It should be noted, however, that if the thermal load on this system increased significantly, the closed loop,sub-cooled nitrogen system with a nitrogen liquefier would become the more economical system. 9. 1.6 Building Requirements Building requirements of the diffusion pump system are listed in Table IX. - 29 -TABLE IX BUILDlt-ilG REQUIREMENTS OF 3211 DtFFUSION PUMP SYSTEM No. Size Weight Power Water Reqd. Equipment Location each each each each 6 3211 D.P. Vault see Fig. 7 6800 lb 20 kW 2.5 gpm stacks 2 Backing Mechanical 4411 H x 1800 1 b 12-1/2 hp 2 gpm pump units Services 5011 X 58 11 Room 9.2 Instrumentation and Controls Each diffusion pump stack will be controlled separately from the vacuum control panel, and the diffusion pump system as a whole will be controlled during normal operation from the main control panel. For instance, valves are controlled as a group from the main control panel, but for testing and trouble-shooting it should be possible to control each valve separately from the vacuum control panel. It is recommended, in general, that remotely control led valves should be automated for closure only and that opening of valves be controlled from the vacuum control panel. In general, valves should automatical-ly close rapidly but be remotely opened very slowly. Throat pressure will be monitored by cold cathode gauges situated in the stack just below the valve, and foreline pressure will be monitored by thermal conductivity gauges. Diffusion pump heater current must be monitored as well as the temperature of the barrel of the pump. Thermostatic control of diffusion pump boiler will be provided. Cooling water flow switches will shut down the diffusion pumps in case of cooling water failure to pump or trap. The backing system will be controlled during normal operation from the main control panel, and during leak testing and maintenance from the vacuum control panel. The system is protected by an automatic slow-bleed valve which effectively prevents oil migration from the rotary pump into the foreline in the case of power failure. The valve should be designed so that the vacuum 1 ines are completely shut before the bleeding operation starts. The backing system will come complete with its own internal controls. In case one half or all of the backing system fails, one half of the complete roughing system can be started and substituted for the backing system. - 30 -Each diffusion pump is fitted with a manually controlled valve on the foreline so that any diffusion pump can be removed for servicing without interrupting the operation of the rema1n1ng pumps. A remotely operated valve could be provided to permit isolation of any diffusion pump from the backing system. Control system procedures in case of emergency are listed in Table X. 9,3 Maintenance Requirements Normal maintenance of the diffusion pump stacks will consist of replacing burned-out heaters, changing diffusion pump oil and replac-ing valve gate seal. The diffusion pumps are fitted with cartridge-type heaters, which are replaceable without dismantling the pump. This can be done during the regular maintenance periods, since the pump will function with one heater burned out. Diffusion pump oil should not require chang-ing more frequently than once a year; polyphenyl ether fluids indicate a 10% decomposition 8 after a dose of 103 Mrad. Therefore, deteriora-tion due to radiation damage in an area where the flux levels are estimated to be about 1.5 Mrad/yr is considered to be negligible. A viton valve gate seal should not require replacement more frequently than once every six months. This is a conservative estimate, since viton suffers 25% radiation damage after a dose of 35 Mrad, and pumps are located where the maximum radiation levels are about 2 Mrad/yr. Maintenance of the backing system will include changing lubrication oil every 1000 hours or as required by deterioration. Shaft seals will require replacement after about 10,000 hours, and V-belt drives should be replaced at 10,000-hour intervals. 9.4 Test Requirements Following assembly in a test stand complete with test dome, the following testing procedure should be followed: 1 ) Test valve operation 2) Test fur leaks 3) Test the base pressure 4) Test the pumping speed 5) Test the oil backstreaming rate The backing system requires a testing procedure similar to that of the roughing system (see Section 8.4). - 31 -TABLE X EMERGENCY PROCEDURES DIFFUSION PUMP SYSTEM 1. Pressure at throat of diffusion pump exceeds 2 x 10- 2 Torr 2. Failure of backing system 3. Failure of electrical power (assuming do not lose instrument air) 4. Failure of cooling water on diffusion pump stack or baffles 5, Failure of LN2 supply 6. Failure of instrument air supply - Close isolation valves - Turn on roughing system - Switch over to roughing system - Close isolation valves (control valve is normally open, energized to close) Switch to potable water supply. If flow not restored, turn off diffu-sion pumps, close isolation valves and cool boilers. - Close isolation valves - Shut off diffusion pumps - Cool diffusion pump boilers Switch to emergency air supply - Close diffusion pump isolation valves Shut down diffusion pumps - 32 -9,5 Operation and Performance The diffusion pumps will be throttled into the system when chamber pressure reaches 2 x 10- 2 Torr and will be fully open at chamber pressures of 1 x 10- 3 Torr. The diffusion pumps will operate during the bake, with temperature rise controlled so that the stack pressure does not exceed 10- 3 Torr. Pumping speeds developed by the diffusion pump stack selected are: mass 2 22,300 1 itres/sec mass 18 38,000 1 i tres/sec mass 28 8,900 1 it res/sec mass 44 24,000 litres/sec Cold traps may be regenerated one at a time by closing the main isola-tion valve, heating the trap and pumping out the desorbed gas with the diffusion pumps. This can be done.without interrupting the operation of the cyclotron. Chamber pumpdown performance is summarized in Figure 5, Chamber pressure distribution is shown in Table IV. It can be seen from the pumpdown curve, Figure 5, that after 15 hours of pumping, the chamber pressure p3 (see Figure 1) corrected for stripping cross-section has been reduced only to 1 ,9 x 10- 7 Torr (based on design gas loads). To reach the required operating pressure, it is necessary to pump for approximately 100 hours until design gas loads have been reduced sufficiently to allow the chamber pressure to approach the required value. As is apparent from the slope of the pumpdown curve in this region, the time of 100 hours is a strong function of the accuracy of the design gas load. During normal operation, oil backstreaming may be as high as 2 x 10- 6 g/min for six 32 in. diffusion pump stacks, depending on trap design. Gross air inrush due to, for example, operator error will cause massive oil backstreaming, an event which is predicted to occur twice in the first year and once every year thereafter. This frequency would not significantly be reduced by additional instrumentation. Closing time for commercially available valves is about 10 seconds -too slow to prevent massive oil backstreaming in case of accidental air inrush. To reduce the closure time significantly would require the use of a special fast-closing valve, perhaps using explosives. Considering the mass of the moving parts, the feasibility of develop-ing a 32 in. valve which will reliably close in a few milliseconds is highly questionable. The diffusion pumps will remain open to the chamber during normal operation. However, after some weeks of operation reduction of gas loads should permit shutdown of one pumping stack on each side of the chamber. - 33 -9.6 Cost Estimates and Suppliers The capital and annual operating costs of the 32 in. diffusion pump system are presented below: Capital costs: 3211 diffusion pump stacks Pumps Traps Valves Mi see 11 aneous Backing system Roughing system Gauging @ $12,300 @ 7,730 @ 13,100 Dry gas source (see Section 12) Cryogenics for 3211 traps Installation, testing and start-up Sub-total Engineering TOTAL $73,800 46,400 78,500 38,900 26,600 30,200 2,000 4,300 43,400 22,000 366,100 42,800 $408,900 The capital costs are based on an NRC diffusion pump combined with a valve and trap supplied by Whittaker Corporation; all components have aluminum foil seals on each flange. Annual operating costs: Technician $ 5,000 Maintenance 3,500 Power and water 6,000 Refrigeration 28,800 Consumables and miscellaneous 4,500 TOTAL $47,800 - 34 -10. 20°K - 80°K CRYOPUMPED SYSTEM 10.1 Cryopumps 10. 1. 1 Cryoarray Concepts The cryoarray will consist of essentially isothermal. surfaces at two nominal temperature levels, 80°K and 20°K. Each surface can condense gases whose partial pressures in the chamber are greater than their vapour pressure at the surface temperature. An 80°K surface can cryopump water vapour and hydrocarbons while a 20°K surface cryopumps all gases except hydrogen, helium and neon. To minimize the costs of supply-ing refrigeration, it is customary to arrange the surfaces so that the 80°K surfaces shield the 20°K surfaces from thermal radiation from visible surfaces at ambient temperature, but still permit gas flow to the 20°K surfaces. Thus, most of the heat load is taken at 80°K and absorbed by a liquid nitrogen cooling (or other) system. The much smaller heat load at the 20°K level is absorbed by circulating gaseous helium provided by a refrigerator. Neon is not normally present in vacuum systems. To cryopump hydrogen continuously surface temperatures of about 4-5°K would be required. The cost of refrigeration at 4°K is about five times that at 20°K; hence, cryopumping hydrogen in large systems is not economically attractive. Helium cannot be cryo-pumped continuously at achievable temperatures. Thus, the combination of cryopumping at 20°K and diffusion pumps to handle the hydrogen gas load is recommended. The use of shield temperatures lower than 80°K would not sig-nificantly reduce the heat load at 20°K, but would increase the cost of refrigeration. Shield temperatures up to 100-ll0°K will not significantly increase the heat load at 20°K and can be tolerated. The convenience of using liquid nitrogen as a coolant generally dictates the use of temperatures of 100°K or less. Cryoarray design criteria include: 1) Pumping speeds of at least 70,500 litres/sec for mass 28 and 840,000 litres/sec for mass 18 2) A minimum heat load at 20°K consistent with (1) above 3) Rugged, leak-tight construction 4) Materials and surface finishes that are unaffected by the radiation environment 5) Space requirements compatible with other cyclotron compon-ents, i.e. resonators, chamber, probes, stripping foil mechanism, beam, etc. The vertical height of the array - 35 -from the chamber wall cannot be greater than 5 in. (as established by the TRIUMF Beam Dynamics Group). The cryoarray should be attached to the lid of the vacuum chamber in order to avoid interference with probes and stripping foil mechanisms. 6) Capability to operate reliably for long periods with weekly defrosting 7) Cooldown to operating temperatures in 2-4 hours 8) Minimum maintenance inside the machine vault 9) Invulnerability to accidental air inrush 10) Reasonable cost Two cryoarray concepts have been considered in detail: the cryol ine shown in Figure 10 and the flat-shield array shown in Figure 11. Preliminary consideration was also given to a chevron array, such as shown in Figure 12. Its characteristics proved to be similar to those of the flat-shield array, but its construction is more complicated. Moreover, the chevron array 20°K surface is inaccessible for inspection or cleaning, and has a high cooldown mass. Therefore, the chevron array was not studied in detail. For both the cryoline and the flat-shield array, molecular and thermal radiation transmission factors from the inlet to the 20°K surfaces and the radiation transmission to all internal 80°K surfaces were determined analytically. The method of analysis consisted of dividing the surfaces into zones, determ-ining view factors between zones assuming diffuse reflections, and solving the equations for flux interchange between zones with a computer program. The possibility of pick-up of RF energy by the cryoarray from the resonators has been considered. However, this effect is negligible, 10since the energy is contained within the hairpin-shaped structure, and stray fields extend for only a few inches from the tips of the resonators. 10.l.l.l Cryoline The characteristics of the cryoline are summarized in Table XI. In determining heat loads the effect of condensate deposits on thermal absorptance of surfaces has been considered. In particular, water vapour condensate on low absorptance surfaces can cause a marked increase in absorptance, 11 - 13 as shown in Figure 13, and result in increased heat loads. For this reason, periodic defrosting of the cryoarray is planned, as frequently as once each week, if required. Hence, the highest - 36 -TABLE XI CRYOLINE CHARACTERISTICS Two arrays, per Figures 10 and 14 Length Capture probability based on Inlet area for gases condensed at 20°K Mass 28 Pumping Speed Mass 18 Pumping Speed 20°K Heat Loads - Two Arrays - 48 ft each array - 0.26 - 70,500 litres/sec each array 1,025,000 1 itres/sec each array (High absorptance = 0.8; low absorptance 0.05) Thermal Radiation from Ambient 1 .6 watts Thermal Emission from 80°K Surfaces Supports TOTAL 80°K Heat Loads - Two Arrays Rear Shield Blocking Plate Supports TOTAL 20°K Cooldown Mass 20°K Cooldown Load 80°K Cooldown Mass 80°K Cooldown Load Clean Surfaces 1738 88 8 1834 watts - 0.9 - 3.0 5.5 watts After One·Week of Operation 2660 352 8 3020 watts - 75 lb - 2,630 (stainless Btu stee 1) 1440 lb (copper and stainless steel) - 47,500 Btu - 37 -heat loads will be encountered at the end of the first week of operation after the chamber has been exposed to ambient atmosphere. During this period the outgassing rate of water vapour is highest, producing the greatest degradation of surface absorptances. Table XI shows heat loads for both clean surfaces and surfaces with water vapour condensate resulting from one week of operation after pumpdown from atmosphere. The two 48 ft lengths of the cryoline can be positioned with-in the vacuum chamber as shown in Figure 14. Alternative arrangements can be considered in the detailed design stage. The position shown is reasonably central in respect to the gas loads and avoids interference with other components. The cryoline components would be fabricated in three or four lengths and assembled in the vacuum chamber. The cryol ine design shown in Figure 10 uses two coolant-carrying tubes as the 20°K condenser. The tubes are held in place by support brackets spaced at 2-3 ft intervals. The cryoline can be constructed using only copper and stainless steel parts. All coolant tubes, support rods and hardware, and the 20°K tubes support bracket are stainless steel; remaining parts are copper. Its high thermal conductivity ensures small tempera-ture gradients in the extended surfaces. The coolant tube dimensions are consistent with the requirements for internal pressure described in Sections 10. 1.2 and 10.1.3. The 80°K coolant tubes would be soft soldered to the copper surfaces to achieve a good thermal bond with a minimum of warping. The stiffeners on the blocking plate. are shown riveted to the plate to eliminate distortion that might be caused by soldering or welding. Considerable care will have to be exercised in fabri-cation and installation to avoid gross distortion of components that could lead to undesirable thermal contacts between 80°K parts and 20°K parts or the chamber wall. The thermal contraction characteristics of copper and stainless steel are well matched, so that stresses or deflections caused by differential thermal contraction would be small when the assembly is at operating temperatures. However, the condenser tubes, the blocking plate and the rear shield will cool down at different rates. To accommodate differential contractions between components during cooldown, the support rod connections should be loose fitting and permit longitudinal sliding. Trans-verse contraction can be accommodated by the flexibility of the support rods. Low absorptance surfaces should be plated with nickel to prevent corrosion and degradation of the absorptance when the surfaces are exposed to the ambient atmosphere. High absorpt-ance surfaces can be blackened by a commercial process which produces a heavy coating of copper oxide. The absorptance of - 38 -0.8 assumed in determining heat loads should be readily achievable. Black paints, which are usually used to produce high absorptance surfaces, are not suitable in the high radiation environment of the cyclotron. The cryoline could also be fabricated using an aluminum con-struction, such as will be described in the next section. 10. 1.1.2 Flat-Shield Array The characteristics of the flat-shield array are summarized in Table XI I. The two arrays would be positioned in the vacuum chamber as shown in Figure 15. The components of each array could be fabricated in two or three lengths, with final assembly being done in the vacuum chamber. The chamber pressure after a pumping time of 15 hours is shown in Table I I I for the flat shield array pumping speeds. The design shown in Figure 11 is based on the use of aluminum alloy (6061) for all parts except the support rods and associated hardware, which would be stainless steel. Extruded aluminum, coolant tubes are welded to the surfaces. The 11D-tube" extruded cross-section faci 1 itates welding, and its dimensions are compatible with the internal pressure require-ments described in Sections 10. 1.2 and 10.1.3. Tbe relatively high thermal conductivity of 6061 aluminum alloy, though not as high as that of copper, will maintain acceptably low temperature gradients in the extended surfaces. Low absorptance surfaces can be readily produced on aluminum by a commercial process known as "bright dipping". High absorptance surfaces can be produced by black anodizing, which results in an oxide coating containing a black inorganic dye. An absorptance of 0.85 is r.eadi ly achievable. Since both coolant tubes and surfaces to which they are bonded are made of aluminum, differential thermal contraction is avoided. However, as with the cryoline, the 20°K condenser, front-shield and rear-shield may cool at different rates, so the support rod connections should permit longitudinal sliding. Here, also, careful fabrication and installation will be required to avoid undesirable thermal contacts. Aluminum-to-stainless-steel transition joints are required in the coolant lines, between the cryoarray and the line penetra-tion through the chamber wall. Such joints are commercially available for cryogenic-vacuum service and can be considered reliable for this application. The flat-shield array could also be fabricated using a copper-stainless steel construction 1 ike that described for the cryol ine. - 39 -TABLE X 11 FLAT-SHIELD ARRAY CHARACTERISTICS Two arrays, per Figures 11 and 15 Length Capture probability based on Inlet area for gases condensed at 20°K Mass 28 Pumping Speed Mass 18 Pumping Speed 20°K Heat Loads - Two Arrays - 34 ft each array - 0.34 - 74,500 1 itres/sec each array - 840,000 1 itres/sec each array (High absorptance = 0.85; low absorptance = 0.05) Thermal Radiation from Ambient - 8.2 watts Thermal Emission from 80°K Surfaces 1 .2 Supports - 4.0 TOTAL 13.4 watts 80°K Heat Loads - Two Arrays Clean Surfaces After One Week _of Oee ration Rear Shield 2148 2898 Front Shield 140 748 Supports 8 8 TOTAL 2296 watts 3654 watts 20°K Cooldown Mass - 75 lb (aluminum) 20°K Cooldown Load - 5,630 Btu 80°K Cooldown Mass - 320 lb (aluminum) 80°K Cooldown Load - 22,400 Btu - 40 -10. 1. 1.3 Test Requirements Thorough testing prior to placement in service is essential for either array. The following tests should be part of material quality control: l) Ultrasonic (or equivalent) inspection of coolant tube material to ensure absence of faults 2) Measurement of the room temperature emittance of samples of high and low absorptance surfaces The following tests should be made with the array fabri-cated in sections: l) Pressure test coolant tubing to l .5 times maximum work-ing pressure. 2) Cold shock each section to liquid nitrogen temperature and vacuum leak test with helium at maximum working pressure inside the coolant tubes. The sections will have to be placed inside a vacuum chamber to properly conduct this test. The following tests should be made after the arrays have been installed in the vacuum chamber: l) Cold shock coolant tubing to liquid nitrogen tempera-ture 2) Pressure test each coolant circuit at 1.5 times maximum working pressure 3) Warm vacuum leak test with helium at maximum working pressure inside each coolant circuit 4) Cold vacuum leak test with helium at maximum operating pressure in each coolant circuit 5) Performance test to determine that required operating temperatures are achieved and that design pumping speed is obtained 10.l.l.4 Reliability With proper detail design, fabrication and testing, both the cryoline and the flat-shield array should be highly reliable over a long period of time. Of particular concern is the development of leaks from the coolant tubes into the vacuum chamber. The copper-stainless steel coolant tube construction, for either concept, would probably offer the maximum reliability in this regard. Stainless steel - 41 -is widely used in vacuum-cryogenic service; leak-tight welded joints are readily produced by qualified welders. A high degree of vacuum integrity can also be achieved with the aluminum construction. Most cryogenic shrouds in high-vacuum space-simulation chambers are made from aluminum. Though welding tube joints is more difficult with aluminum than with stainless, leak-tight welds are readily produced by qualified welders. The testing procedures described above would reveal any leaks and permit their repair. Experience has shown that once a system is proved leak tight, it will remain so for years of service. The ability of the cryoarray surfaces to retain their thermal absorptance properties is also of concern. Polished or anodized aluminum surfaces and nickel-plated copper surfaces should withstand the radiation environment without degradation. The durability of the blackened copper surfaces is not known at this time and should be further investigated. 10.1.1.5 Cost Estimates 10.1.2 The estimated installed costs of the cryoarray concepts are: Cryoline (copper-stainless steel construction) $73,800 Flat-shield array (aluminum construction) $65,100 Breakdown of costs is indicated below: Flat-shield Array C ryo 1 i ne Design, 1 i a i son, engineering supervision $16,300 $16,300 Materi a 1 s and fabrication 34,300 40,000 Shipping, installation and field test 14,500 17,500 TOTAL $65,100 $73,800 The higher cost of the cryoline is a result of higher material costs and its longer length. 20°K Coolant Circuit A schematic diagram of the 20°K coolant circuit is shown in Figure 16. The 20°K coolant tubes of the two arrays would be connected in series. The pressure relief devices - 42 -at the inlet and outlet of each array are for emergency venting (see section 10. 1.2.5). About 320 ft of well-insulated transfer line will be required to interconnect the two arrays with the remotely placed 20°K refrigerator. The requirements for this 1 ine are stringent: 1) Exposure to high radiation levels over most of the length 2) Extremely low heat leak 3) High reliability over a 10-year period 4) Ready replacement in the event of failure 5) Low cooldown mass 6) Reasonable cost Vacuum-jacketed lines will be required to obtain a suffi-ciently low heat leak. Two types have been considered: vacuum-jacketed line with multilayer insulation (VJMLI), and vacuum-jacketed line with a liquid nitrogen cooled shield (VJLNS). 10.1 .2.1 VJMLI Transfer Line A feasible line configuration is shown in Figure 17. Each section of line 'is short enough to be taken through the cyclotron vault access passageway. The cross-section of the line and of a typical bayonet disconnect are shown schematically in Figure 18. A 3/4 in. o.d. inner tube with 0,035 in. wall thickness will circu-late the required coolant flow rates for any of the refrigerators being considered with low pressure drop, and will withstand internal pressures that may be encountered under any conditions. A thinner wall would be desirable to reduce the cooldown mass, but manufacturers of such lines do not consider a thinner wall feasible. The inner tube is held in place by insulating spacers, placed at intervals along the length of the line. The characteristics of the VJMLI line are summarized in Table XI I I. TABLE XI 11 VJMLI 20°K TRANSFER LINE CHARACTERISTICS Estimated 20°K Heat Leak 320 ft of 3/4 11 line 19 bayonet couplings Elbows and tees 20°K Cooldown Mass 20°K Cooldown Load 52 watts 33 ..1. 92 watts 92 lb (stainless steel) 3200 Btu - 43 -Vacuum-jacketed lines are most commonly fabricated in sections with bayonet couplings at both ends, baked, evacuated and valved off at the factory. The sections are assembled into a circuit at the site. According to the manufacturers, a well-constructed line section can operate for years without re-evacuation. This is partic-ularly true for a 20°K coolant line,which during operation is cryopumped. Standard practice is to include a gauge in each section of the line, for periodic check-ing of the vacuum, and a pump-out valve that enables connection of a pumping system in the event re-evacuation is required. The high radiation level in the cyclotron vault imposes unusual requirements for most of the line. Standard construction uses plastic spacers between inner and outer tubes and elastomer seals at the bayonet couplings. Both must be eliminated in this case. It is anticipated that the plastic spacers could be replaced by glass, ceramic or stainless steel spacers of special design, with no significant increase in heat leak; the bayonet joints could utilize metal seals. The primary effect of these adaptations will be to increase the cost. All sections of line should be subjected to the following tests before installation: 1) Cold shock inner tube 2) Pressure test inner tube-at 1.5 times maximum working pressure 3) Vacuum leak test with inner tube cooled to 80°K, then pressurized with helium gas to maximum working pressure, and exterior jacket enveloped in helium gas at one atmosphere After the line is installed, a performance test to deter-mine the steady-state heat leak and pressure drop associated with the line should be made before its acceptance. VJMLI transfer line made by an experienced manufacturer should exhibit a high degree of reliability. Re-evacuation should be required infrequently, if at all, for this service. In the event a section of line loses vacuum and cannot be re-evacuated, its replacement would not be difficult because of the relatively short sections of line comprising the overall assembly. - 44 -Installed cost estimates for the VJMLI transfer line are as fol lows: 320 ft of 3/4'' line with elbows and tees 19 bayonet couplings Adaptation of above items to high radiation level environment Installation TOTAL $12,200 l ,550 9,000 2,800 $25,550 The estimates include an allowance for adaptation of the lines to the high radiation level in the cyclotron vault. 10. 1.2.2 VJLNS Transfer Line This type of line is of interest because of its potential-ly low heat leak. It utilizes a thermal radiation shield, cooled to 80°K, between the 20°K coolant tube and the outer vacuum jacket. Two alternative types of construction can be identified: 1) A line assembled from bayonet-connected sections, each short enough to pass through the cyclotron vault access passageways, i.e. similar to the VJMLI configuration described above. 2) A line with bayonet joints only at the ends, to facilitate attachment to the refrigerator and raising the top of the vacuum chamber. All other joints in the inner and outer tubes would be welded at final assembly, and the line evacuated. The first type of construction represents the least departure from common practice, in that the sections of line could be fabricated, evacuated and sealed at the factory. The heat leak, with this line, will be substan-tially less than for the VJMLI line, because radiation heat transfer to the inner tube is virtually eliminated. The second type of line could have an even lower heat leak, because it eliminates a number of bayonet joints. Because of its built-in construction, trouble-shooting and repair or replacement of a section would be difficult. A vacuum pumping system will be required for initial evacuation and periodic re-evacuation. It could be located at the - 45 -refrigerator end of the line. The built-in line is expected to be more costly than the bayonet-connected, due to the difficult nature of on-site assembly and testing. Enquiries were made of two experienced manufacturers of transfer line with regard to the feasibility, performance and cost of a VJLNS line for this application. CVI Corporation acknowledged that such a line is feasible and expressed an interest in building it. However, they felt that its cost would be high in relation to the savings associated with reduced heat load. Cryogenic Engineering Company (Cryenco) also expressed an interest in building the line. They proposed a concept using bayonet-connected sections and provided estimates of heat leak and cost. A cross-section of the Cryenco line is shown in Figure 19. A typical bayonet connection is shown schematically in Figure 20. Based on the lin·e configuration of Figure 17 the line would have the characteristics shown in Table XIV. TABLE XIV VJLNS 20°K TRANSFER LINE CHARACTERISTICS Estimated 20°K Heat Leak 320 ft of 3/4 11 line Bayonet couplings 20°K Cooldown Mass 20°K Cooldown Load Estimated 80°K Heat Leak 11 watts li 44 watts 92 lb 3200 Btu 310 watts The heat leak is primarily due to the bayonet connections. Somewhat reduced heat leak could be achieved with longer sections between joints. The acceptable maximum section length will be determined by the access passageway to the cyclotron vault. Each section of line would include a gauge for periodic checks of the vacuum level and a valve to permit re-evacuation, if required. The testing of the VJLNS line would be similar to that for the VJMLI 1 ine. The following tests should be carried out before installation at the site: - 46 -1) Cold shock inner tube and radiation shield coolant tube 2) Pressure test both tubes at 1 ,5 times maximum working pressure 3) Vacuum leak test with both tubes cooled to 80°K, then pressurized with helium gas to maximum working pressure, and exterior jacket enveloped in helium gas at one atmosphere After the line is installed, a performance test to deter-mine the steady-state heat leak at both 20°K and 80°K and the pressure drop associated with each circuit should be made before its acceptance. The construction of the VJLNS line is more complex than that of the VJMLI line; more joints are exposed to the vacuum, and bellows will be required, as shown in Figure 20. The likelihood of leaks developing in a vacuum-jacketed line is related to the number of joints and/or bellows exposed to the vacuum. Hence, the reliability of the VJLNS line for long-term service may be somewhat less than that for the VJMLI line. Nevertheless, it is believed that with proper design and fabrication, and thorough testing, this type of line will be reliable. The estimated installed cost of the VJLNS line described above and based on a line configuration like that in Figure 17 is $40,000. This •includes an allowance for adapting the construction to the high radiation level. 10. 1.2.3 Circuit Cooldown Time Estimated cooldown times for the 20°K circuit are shown in Table XV for initial temperatures of 300°K and 230°K; the latter temperature corresponds to the condition immediately TABLE XV 20°K CIRCUIT COOLDOWN TIME Basis: Circuit consists of 320 ft of VJMLI or VJLNS transfer line connected in series with two arrays Initial Cooldown Time - h Temperature (Refrigerator) Array OK PGH-105 Airco 'A' Cryoline 300 5.6 0.6 Cryoline 230 3.6 0.4 Flat-shield 300 8.5 0.8 Flat-shield 230 5.5 0.5 - 47 -after defrosting. The table is based on the assumption that the refrigerator is cooled down prior to circuit cooldown and that the transfer lines and arrays will be cooled down together. Pre-cooling the transfer lines to reduce the cool-down time achievable with the PGH-105 refrigerator was considered. The addition of the four valves and associated couplings, to permit circulating cold gas through the lines with the arrays by-passed, would cause the 20°K steady-state heat load to exceed the capacity of the refrigerator. Hence, pre-cooling the lines is not possible with the PGH-105; with other refrigerators it is not necessary. 10. 1.2.4 Loss of 20°K Refrigeration If 20°K refrigeration is lost as a result of refrigerator shutdown, warm-up of the 20°K condenser can be retarded by: 1) immediately stopping gas circulation to prevent the transfer line heat leak contributing to condenser warm-up, and 2) maintaining pressure in the coolant tubes to maximize their thermal capacity. Assuming these steps are taken, warm-up of the flat-shield array condenser to 30°K, as a result of the thermal radiation heat load, would occur in 10-15 minutes. The cryoline condenser warm-up to 30°K would take more than 1.5 hours, due to the larger helium content and lower heat leak. The equilibrium vapour pressure for nitrogen is 3 x 10- 5 Torr at 30°K .. As the condenser temperature and nitrogen vapour pressure increase further, heat transfer by gas conduction would become significant. The heat load would increase, and the rate of temperature rise would accelerate. If the diffusion pumps were valved off so that no other pumping of nitrogen occurred, the maximum one-week accumulation of nitrogen condensate (about 1000 Torr litres of gas) would be evaporated when the condenser surface reached 38°K, bringing the chamber pressure to 1.2 x 10-2 Torr. To minimize further warm-up, the evaporated condensate should be pumped out as quickly as possible, to bring the pressure below 10- 5 Torr and eliminate heat transfer via gas conduction. 10. 1 .2.5 Accidental Air Inrush Rupture of a feedthrough, window or other such component of the cyclotron vacuum chamber would cause a large inrush of air and a rapid rise in pressure. Abundant thermal energy would be available for warming up the 20°K condensers; but the rate of warm-up will be limited by heat transfer. Analysis has shown that warm-up of the condensers and the helium in the coolant tubes to about 80°K could occur very 10. l. 3 - 48 -rapidly, i.e. in seconds, because of the air condensation on the surfaces and the resulting high heat transfer rate. Further warm-up would be at a much slower rate. The integrity of the 20°K coolant circuit can be maintained under these conditions if: 1) The coolant tubes on the array are designed for a maxi-mum pressure of 5 times the normal operating pressure 2) Pressure relief burst discs to relieve at 1.5 times normal operating pressure are provided at the inlet and outlet of the coolant circuit for each array, as shown in Figure 16 3) The inner tube of the transfer lines is designed for a maximum pressure of 2 times the normal operating pressure The relief devices will cause the pressure in the array coolant tubes to drop after the maximum design value is reached and will protect the transfer lines from overpressure. The coolant tubes described for both the cryoline and flat-shield arrays and for the transfer lines meet the above design criteria with stress levels that are equal to or less than 2/3 the average yield strength of the tube material. With this conservative design the 20°K circuit should survive an accidental air inrush with no damage other than rupture of pressure relief burst discs. 80°K Coolant Circuit A schematic diagram of the 80°K coolant circuit is shown in Figure 21. The valves are for balancing the coolant flow in the parallel branches of the circuit. The pressure relief devices will limit the overpressure under emergency condi-tions (see Section 10.1 .3.6). The requirements for the transfer line in the circuit are as follows: 1) Must be able to withstand high radiation levels over most of length 2) Low heat leak 3) High reliability over a 10-year period 4) Ready replacement in the event of failure 5) Rapid cooldown 6) Reasonable cost - 49 -The economic, steady-state heat leak for S0°K lines can be much higher than for 20°K lines, due to the lower cost of refrigeration at S0°K. Cooldown mass is also not as cri ti ca 1. We have considered three types of transfer lines: 1) Rigid vacuum-jacketed lines (VJR) 2) Semi-flexible vacuum-jacketed lines (VJSF) 3) Bulk insulated lines 10.l .3.1 VJR Transfer Line A feasible line configuration is shown in Figure 22. The line sizes shown permit rapid cooldown and low steady-state pressure drop. The construction of this line is the same as the VJMLI line, except that the multilayer insulation is omitted. The characteristics of the VJR line are summarized in Table XVI. TABLE XVI VJR S0°K TRANSFER LINE CHARACTERISTICS Component 230 ft of 1.5 11 line with elbows and flex sections 110 ft of 111 line with elbow~ and tees 12 - l . 5' 1 bayonet coup 1 i ngs 12 - l II bayonet coup 1 i ngs 4 - l II va 1 ves Estimated S0°K Heat Leak 524 watts 157 112 100 .J.1. 910 watts The vacuum instrumentation, test requirements and reliability are the same for this line as for the VJMLI line. A cost estimate for the VJR line, based on the configuration of Figure 22, is as follows: 230 ft of 1.5 11 line with elbows and flex sections 110 ft of 111 line with elbows and tees 12 - 1.5 11 bayonet couplings $12,700 5,000 5,000 (carried forwcrd 22,700) - 50 -(brought forward 22,700) 12 - 111 bayonet couplings 4,300 4 - 111 valves 2,300 Adaptation of above to high radiation level environment 10,000 Installation 2,BOO TOTAL $42,100 10. J.3.2 VJSF Transfer Line The construction of a conmercially available line of this .... type" is indicated schematically in Figure 23. The inner and outer tubes ~re made of copper tubing with a helical corrugation that provides enough flexibility to accommodate thermal contraction of the inner line and permits moderate bends. The standard line has a twisted-Teflon-strip insulating spacer, but the manufacturer can provide a non-plastic spacer suitable for the high radiation level environment. The line is sold in lengths with bayonet (or other type) couplings at both ends. No provision is made for sorbing or gettering gases in the vacuum space; to realize the low heat leaks published by the manufacturer, it is necessary to provide continuous vacuum pumping. A possible configuration for a VJSF B0°K transfer line is shown in Figure 24. Because of its flexibility, long sec dons of the 1 i ne could be taken into the eye 1 ot ron vault. Therefore, fewer joints are required. The performance characteristics of VJSF transfer line are summarized in Table XVI I. The line heat leaks shown in the table are higher than the manufacturer's published values, for standard line, to account for the incorporation of non-plastic spacers. TABLE XV 11 VJSF B0°K TRANSFER LINE CHARACTERISTICS Estimated B0°K Component 330 ft - 1.511 line with tees l O - 1. 511 bayonet coup 1 i ngs 4 - 111 bayonet coup 1 i ngs 4 - 111 va 1 ves *Semiflex™ 11A11 , by Vacuum Barrier Corporation Heat Leak 410 watts 94 34 _u_ 555 watts - 51 -The design internal pressures for Semiflex™ 11A11 published by the manufacturer are as follows: Inside Diameter in. 0.65 1.25 1.73 2.21 Design Pressure psi 175 150 125 85 The manufacturer reports that bursting of the inner line does not occur until much higher pressures are reached, 560 psi for the 2.2 in. i.d. line. Nevertheless, it seems reasonable to follow the manufacturer's suggested design pressures and exclude this line from consideration where coolant pressures exceed the above values. Where use of the VJSF line can be justified, it should be subjected to the same tests as the VJR line. The somewhat limited experience with this type of line in service has shown it to be reliable. The manufacturer states that, to his knowledge, no vacuum leaks have occurred in the field. In the event of failure or greatly degraded performance, the flexibility of the line would make it easier to replace than other types. Cost estimates for the VJSF line are shown below. At the manufacturer's suggestion, a factor of 2.5 has been applied to costs per unit length of standard line to account for the incorporation of the non-plastic spacers. 330 ft - 1.5 11 I ine with tees 10 - 1 .5 11 bayonet couplings 4 - I" bayonet couplings 4 - 111 valves Vacuum pump Installation TOTAL 10. 1.3.3 Bulk Insulated Transfer Line $ 9,100 6,600 2,100 2,300 700 2 2800 $23,600 The high radiation level rules out the common low-initial-cost approach of polyurethane foam insulated lines. However, use of other bulk insulations, such as fibreglass, perlite, etc., is feasible. The line configuration would - 52 -be similar to that for the VJR line shown in Figure 22. An all-metal construction suitable for the high radiation level is shown schematically in Figure 25. The outer metal tube serves as a vapour barrier to prevent permeation of atmospheric moisture into the insulation and resulting loss of insulating effectiveness. The insulating space would be charged with one atmosphere of dry nitrogen. Line sections between joints could be fabricated and sealed up by the supplier, with joints assembled on the site. The outer diameter of the insulation should be about 3-4 times the coolant tube diameter to limit water condensation on the outer jacket. The characteristics of a bulk insulated line, such as that shown in Figure 25, are summarized in Table XVI I I. TABLE XVI 11 BULK INSULATED 80°K TRANSFER LINE CHARACTERISTICS Insulation Effective thermal conductivity Ratio of insulation & tube diameters Heat leak per unit length Heat leak to 330 ft of 1.5" I ine fibreglass 0.02 Btu/(h ft °F) 4 36 Btu/(h ft) 11,900 Btu/h = 3490 W The cost of a bulk insulated line is difficult to assess because it would be a custom designed and built line without the usual plastics, adhesives or mastics. Considering the type of construction required, the large diameter of the outer jacket, the requirement for flexible sections in both inner and outer lines to accommodate thermal contractions, and the field-made joints, it is expected that the cost of this line will not be substantially less than that for a VJR 1 ine. The bulk insulated 1 ine should be very reliable, since it does not require maintaining vacuum in the insulating space. However, because of its high heat leak and poor prospects for an offsetting low initial cost, this line does not appear attractive. 10. 1.3.4 Circuit Cool down Time Circuit cooldown with liquid nitrogen can be rapid. Detailed analysis has shown that if liquid nitrogen is supplied to - 53 -the circuit inlet at 30 psig, the transfer line and B0°K surfaces of the array (either type) can be cooled to operating temperatures in about 45 minutes. Approximately 300 litres of liquid nitrogen would be evaporated in the cooldown process. Cooldown of the circuit with a helium gas refrigerator will depend on the capacity vs. temperature characteristics of the unit. The line sizes in the B0°K circuit and the parallel branch arrangement should permit high circulation rates and good utilization of the refrigerator capacity during cooldown. 10. 1.3.5 Loss of B0°K Refrigeration Analysis shows that following refrigerator shutdown the radiation heat leak onto the surfaces would warm them to 173°K, where the vapour pressure of water is 1 x 10-s Torr, in about 40 minutes. (It should be noted that carbon dioxide would not condense on the B0°K surfaces, due to its low partial pressure during normal operation.) The heat load on the 20°K condensers would increase, but the 20°K refrigerator should be able to maintain the temperature low enough to prevent gross evaporation of condensate. Further warm-up of the surfaces would raise the water vapour pressure and cause gas conduction to become a significant mode of heat transfer. The heat load would increase and the rate of temperature rise would accelerate. When the surfaces reached about 230°K the water vapour condensate would be completely evaporated and, assuming none was pumped off during warm-up, the chamber pressure would be 0. 11 Torr. Simultaneous evaporation of the nitrogen deposit on the surf-aces initially at 20°K would make little difference in this pressure level. If the 80°K refrigerator can be brought back on-stream, or an emergency cooling system put into operation in about 40 minutes, operation could be resumed without gross evapora-tion of condensate deposits. 10. 1.3.6 Accidental Air Inrush Initial warm-up of the B0°K surfaces in the event of a massive air inrush would be much slower than that of the 20°K surfaces, due to the higher specific heat of metal surfaces at B0°K and the absence of air condensation and associated high heat transfer rates. Nevertheless, pressure relief burst discs should be placed, as shown in Figure 21, to mini-mize the overpressure in the array coolant tubes and to protect the transfer lines from overpressure. Analysis has shown that for a subcooled liquid nitrogen coolant circuit operating at 50 psia, with burst discs that relieve at 80 psia, array coolant tubes designed to withstand a maximum internal pressure of 400 psia could withstand accidental air ---------------- 54 -inrush without damage. For a helium gas coolant circuit, the maximum pressure would be that at which the burst discs ruptured. 10.1.4 Operating Procedures 10. 1.4. 1 Cool down 10. l. 4.2 To shorten cooldown time both the S0°K and 20°K refrigerators should be cooled internally prior to circuit cooldown. Simultaneous cooldown of S0°K and 20°K surfaces can commence when the pressure in the chamber is reduced to about 10-2 Torr. The 80°K surfaces will cool down faster; residual water vapour will condense on them rather than on the 20°K surfaces. Full pumping speed for water vapour will be achieved when the surfaces reach a temperature of about 130°K. The full pumping speed for mass 28 will not be achieved until the condenser is at 20°K. Period i c Defrost It has been determined that weekly defrosting of the cryo-pumping surfaces is compatible with the operating schedule of the cyclotron, provided it can be accomplished in about eight hours. Periodic removal of condensed deposits is highly desirable to maintain low thermal absorptances on certain surfaces and control the maximum heat loat. Defrost-ing can be accomplished as follows: 1) Warm 20°K surfaces to 34°K and hold at that temperature. Nitrogen vapour pressure is 10-3 Torr at 34°K. The nitrogen condensate can be pumped off by the diffusion pumps in a few minutes at that pressure level. 2) Continue to warm the 20°K surfaces and begin warming the 80°K surfaces after nitrogen is removed. Warm both to about 230°K to drive off water vapour. Water vapour may be pumped onto liquid nitrogen traps of diffusion pumps. 3) After water vapour is pumped from the chamber and pressure has been reduced to 10-2 Torr resume cooldown of S0°K and 20°K circuits to operating temperatures. 10. 1.4.3 Maintenance Under normal circumstances the array should require no maintenance. In the event of an accident some maintenance may be required. For example, high heat loads could be caused by contaminated low emittance surfaces. Visual inspec-tion of the array would indicate such contamination and the surfaces would have to be cleaned off. Both the cryoline and flat-shield arrays have relatively accessible surfaces for inspection and cleaning. - 55 -Maintenance of the transfer lines will be preventive and should include: 1) Periodic check of the pressure in the vacuum jacket of each section of 20°K and 80°K transfer line 2) Routine maintenance of any vacuum pumping systems for transfer lines, i.e. change of oil, etc. 3) Visual inspection of all burst discs to ensure workability If poor vacuum in the transfer line jackets causes the heat leak to reach unacceptable levels, the degraded line section(s) would have to be re-evacuated. - 56 -10.2 Cryogenic Generators The cryogenic arrays will be cooled and maintained at operating temperatures of 20°K and B0°K (nominal) by means of a cryogenerator. Requirements of the refrigeration system include: 1) Adequate capacity at 20°K and B0°K for cooldown and steady-state operation 2) Reliability consistent with the proposed cyclotron operating schedule 3) Maintainability 4) Reasonable requirements for space, power, water, etc. 5) Reasonable cost The reliability requirement dictates that proven refrigeration systems, or at least systems based on proven components, be utilized. Thus, the selection of a refrigerator is a strong function of discrete units available. The 20°K thermal load predominates during the process of refrigerator selection. An electric drive, modified Stirling cycle machine rated at 60 watts nominal (47 watts guaranteed) at 20°K is available from Philips Electronic Industries. Several machines are available in the range of 100 to 500 watts at 20°K. These machines are three basic types: 1) Electric drive, modified Stirling cycle machines (Phi 1 ips) 2) Machines utilizing reciprocating expanders in conjunction with reciprocating compressors (500 Inc.) 3) Systems utilizing turbine expanders in conjunction with reciprocating compressors (Airco Cryogenics Inc., British Oxygen Cryoproducts) Turbine expanders have in the past few years been extensively applied to industrial cryogenic applications such as air separation plants and natural gas liquefaction plants. Industrial experience has, in general, demonstrated superior reliability and reduced maintenance· for turbine expanders. The significant features of turbine expander units are: 1) Inherently high reliability of the small, simple, rotating turbine (which may not, however, be attained because of unreliable ancillary equipment) - 57 -2) High capacity at temperatures above steady-state operating temperature, thus producing a short cooldown time 3) Initial costs equal to or less than comparable reciprocating expander units 4) Susceptibility of turbine to damage from contaminants in the gas stream 5) Susceptibility of turbine to failure of gas bearings, particular-ly during start-up The closed-cycle system proposed for the TRIUMF application significantly reduces the susceptibility of the turbine to contam-inants in the gas stream. The long run time (six months) required reduces the susceptibility of the turbine to failure of the gas bear-ings during start-up. Thus, turbine expander systems have been considered, in comparison with other systems, for the cryogenic generator. The requirement for refrigeration at 80°K may be satisfied by commer-cial supply of liquid nitrogen, by a closed-cycle refrigeration system or a combination of the two. An electric drive, four cyclinder modified Stirling cycle machine rated at 3200 watts (nominal) at 80°K is available from Philips Electronic Industries. A preliminary economic analysis has established that the use of commercial liquid nitrogen is not attractive, except as a stand-by to cover refrigerator outage. The thermal load at both 20°K and 80°K may be satisfied by an inte-grated refrigeration system. Such an approach offers the potential advantage that redundant mechanical units required for reliability can then serve both the 20°K and the 80°K loads. 10.2. I Cryogenerator Configuration The developed concepts of cryogenic arrays, transfer lines and refrigeration systems have evolved into the configurations shown in Table XIX. Configurations I and I I have been devised to take advantage of the low 20°K load of the VJLNS transfer line. Configura-tions I I I and IV are systems using separate cryogenerators for the 20°K and 80°K loads. Configurations V and VI investi-gate the possibility of supplying the 20°K and 80°K load requirements from an integrated system. CON FIG. A2.RAY T. L.. TYPE 20° K TYPE 20°K so•K "1!.l!AY. T. L.. I CJl:.YOLJNE VJL.N.S SF)(. "' .32 11 l=L.AT SHIELD VJLNS 5Fl'. 14 32. lJI C.R.Y0L-iNE VJML.l SFlt " 92 Bl l'L"T !HIEU> VJlollL..l SF><. 14 92 y C"'-YOLINE VJML.l SF)r. " ~2. 1ZI. FLAT SHIELD VJMLI si=x 14 92. TABLE XIX ALTERNATIVE CRYOSYSTEM CONFIGURATIONS L-OAD -W 20°1<. eo°K LOAD- w VALVE.';, TOTAL. 2.EFl!.IGEt"TOf /\£.1!'..AY 80°1<. T.L. 2.0"K T. L.. COLO T2.1'PS 20°K ,::[Fl'.IGE2.,_T02 e 4/o e. • PHILIPS .!1020 S55 310 325 --&-P<.H • 105 8 54 -e- 3(;50 555 '.:!)10 325 -e----- 98 .,._,eco •A.• 302.0 S55 --Q- 325 ---&- IOIO A1e.co • A.' .31#50 555 ......... .325 --a---&-- ee A12.CO • C. 1 30-Z.O <o"!.O --a- 32.~ --e---&- IOCo All'.CO 'C"' .3'-50 c..ao -- 32.S -9-L.N-. LN;o LNa TANK. ~E.TUeN CIR.CUL" TIMI PUMP P"UMP T. L., 195 41S 1,220 ISS 415 1,2'2.0 19 S" 415 1,52.0 195 415 1,520 ,~s; ISO 1,01oo i.95 160 l,OG,O - -TO"TAI. Co,040 '°•" 70,,030 6, (oG,0 5,380 G,010 ao•K 2.E.Fli:IGE~",.oc 2-PHIL..IPS. PPG-400 2 • PHILIPS. PPG-400 2.·PHILIPS PP6·40o 2. ·l"'IIIL.IP'=> PPG-400 !>-12.CO •c • A.1ec..o • c"' V, co - 59 -Configuration I Calculated thermal load for configuration I is 46 watts at 20°K and 6040 watts at 80°K. • The refrigeration system is shown schematically in Figure 26. Refrigeration at 20°K is provided by two Philips PGH-105 units, so connected that both units will operate during cool-down and either unit may carry the steady-state load. The second, stand-by cryogenerator is necessary to meet the reliability requirements and reduce cooldown time. Valves at the inlet and outlet of each machine are necessary so that the machine which is not in service may be dismantled for maintenance or repair. It would be desirable to utilize the transfer line configuration shown in Figure 17, and simply add required isolation valves. However, addition of four vacLWm-jacketed valves and associated fittings increased the 20°K load by 10 watts, for a total load of: Arrays VJLNS transfer line 4 valves and fittings 6 44 10 60 watts (Valves with a heat leak much lower than 3 watts are being developed by UBC Physics Department but are not yet proven.) This load is equal to the "nominal" capacity of the Philips PPG-105 unit and significantly exceeds the guaranteed capacity of 47 watts. Further, machine capacity is reduced during operation, due to oil contamination of regenerator (see Section 10.2.3). It is not prudent to depend on the unit to exceed the guaran-teed capacity, and it therefore is necessary to reduce the load at 20°K. This may be accomplished by eliminating some of the bayonet couplings in the VJLNS transfer line. A possible configuration is shown in Figure 27. Construction of the cyclotron is feasible with such a configuration, but removal of the precast concrete vault roof beams would be required for replacement of sections of the transfer line. The 80°K requirements are supplied by a closed circuit, sub-cooled liquid nitrogen system utilizing two Philips PPG-400 machines as nitrogen re-condensers and commercial liquid nitrogen supply to cover machine outage. The liquid nitrogen storage tank contains 5000 US gal of liquid nitrogen, which will supply the full 80°K load (i.e. loss of both refrigerators) for about 72 hours. It wi 11 be necessary, - 60 -before the tank contents are consumed, to obtain a delivery of liquid nitrogen from a commercial supplier. Liquid nitrogen is available, on a bulk-delivery basis, from at least two suppliers in the Vancouver area. It would be reasonable to negotiate a supply contract for regular refill of the liquid nitrogen storage tank and for priority deliveries on 48 hours' notice. The proposed location and typical dimensions of the liquid nitrogen storage tank are shown in Figure 28. A horizontal liquid nitrogen tank of similar dimensions could be obtained for little, if any, additional cost. It will be necessary, for delivery by the liquid nitrogen supplier, for a standard 40 ft semi-trailer to drive to within a few feet of the control cabinet of the storage tank. Liquid nitrogen is vapourized in an ambient air heat exchanger and led to the liquid nitrogen traps and 80°K pump. It is used to expel liquid during the regeneration sequence and system shutdown. The liquid nitrogen circulating pump is an electrically-driven turbine pump with balanced shaft seal and long-service bearings. A stand-by pump is provided to allow maintenance of the pumps without interrupting operation of the 80°K array. The pumps are located at the base of the tank to obtain adequate NPSH. The 80°K cryogenerators, located in the mechanical services room, are supplied with nitrogen vapour by means of a VJSF transfer line. Condensed nitrogen drains, by gravity, into the liquid nitrogen accumulator. When the liquid nitrogen accumulator is full, the liquid nitrogen return pump is auto-matically started to return the liquid nitrogen to the storage tank. If the 80°K refrigerators (nitrogen condensers) were located at an elevation a few feet above the top of the storage tank, the condensed nitrogen could drain directly into the storage tank, thus eliminating the need for the liquid nitrogen accumulator and return pump. However, it appears that no suitable building space is available. It would be possible, subject to site conditions, to provide a concrete-lined pit for a horizontal liquid nitrogen storage tank, so that the top of the tank is at an elevation of about 255 ft. A preliminary estimate indicates that the cost of lowering the tank cannot be justified by the elimination of the liquid nitrogen accumulator and return pump. The space requirements, weight, and power and cooling water requirements of the components of configuration I are shown in Table XX. TABLE XX BUILDING REQUIREMENTS OF COMPONENTS OF CONFIGURATION I Cooling Number Size Weight Power Water Component Required Location (each) (each) (each) (each) 1 b hp USgpm 20°K Cryogenerator 2 Mechanical services 6711 H x 3811 x 2011 700 15 3,3 (Phi 1 ips PGH-105) room + 3611 O.H. Q'\ 80°K Cryogenerator 2 Mechanical services 6511 H X 3611 X 7211 2,200 38 13.5 (Philips PPG-400) room + 7211 O.H. LN2 Accumulator and 1 Mechancial services 4811 H X 3011 X 3011 300 1.5 -Return Pump room + 3611 O.H. LN2 Storage Tank 1 Outside building 28011 H x 10811 x 13211 empty - -(5,000 USgal) (accessible by truck) + 3611 O.H. 24,000 ful 1 58,000 LN2 Circulating Pump 2 At base of LN2 tank 3611 H x 1411 x 1611 300 1.5 -+ 3611 O.H. - 62 -Configuration I I Configuration 11 is an attempt to combine the smal 1 (and economical) Philips PGH-105 cryogenerator and the lower cost flat-shield array. However, even with VJLNS transfer lines, and the "minimum" number of bayonets per Figure 27, the calculated load at 20°K is 54 watts, which exceeds the guaranteed 47 watts for the proposed refrigerator. Thus, the configuration is not feasible. Configurations I I I and IV Configurations I I I and IV are systems utilizing separate refrigerators for the 20°K and 80°K load and the lower cost VJMLI 20°K transfer line. The configurations are shown schematically in Figure 29. The 20°K cryogenerator operates on a closed helium cycle and utilizes a turbine expander and reciprocating compressors. Developed cryogenerators of this type are available from Airco Cryogenics Inc. and British Oxygen Cryoproducts. A comparative analysis of this machine and a machine using a reciprocating expander and reciprocating compressors estab-lished the superiority of the turbine expander system on the basis of capital cost, operating cost and reliability. The 20°K cryogenerator incorporates a stand-by compressor and a stand-by turbine expander. Liquid nitrogen is used to cool the refrigerator during start-up, but no liquid nitrogen is required during steady-state operation. The 80°K system is similar to that of configuration I. Building requirements of the components of configurations I I I and IV are shown in Table XXI. Configurations V and VI Configurations V and VI represent an investigation of the possibility of supplying both the 20°K and 80°K load from one integrated cryogenerator. The refrigeration system is shown schematically in Figure 30. The 20°K array is cooled by circulating helium gas at 150 psi in a closed circuit, through VJMLI transfer lines. The 80°K load is handled by a sub-cooled liquid nitrogen system. Helium at 80°K (nominal) is circulated from the refrigerator through VJR transfer lines to the liquid nitrogen storage tank where it passes through a heat exchanger, then TABLE XXI BUILDING REQUIREMENTS OF COMPONENTS OF CONFIGURATIONS I I I AND IV Number Size Weight Component Required Location (each) (each) I b 20°K Cryogenerator (Ai rco 11A11 ) Compressor 2 Mechanical services 6011 H x 4811 x 7211 2,500 room + 4811 O.H. Cold Box 1 Mechanical services 8011 H X 4811 X 4811 2,000 room + 8011 0. H. He accumulator I Outside building 4811 H x 205•• x 4011 3,500 80°K Cryogenerator 2 Mechanical services 6511 H x 3611 x 7211 2,200 (Philips PPG-400) room + 7211 O.H. LN2 Storage Tank 1 Outside building 28011 H X 10811 X 13211 empty (5,000 USgal) (accessible by truck) + 3611 0. H. 24,000 fu 11 58,000 LN2 Circulating Pump 2 At base of LN2 3611 H X 1411 X 1611 300 + 3611 O. H. LN2 Accumulator and 1 Mechanical services 48" H X 3011 X 3011 300 Return Pump room + 3611 0. H. Power (each) hp JOO --38 -1.5 1.5 Cooling Water (each) USgpm 2 --13.5 ---O' \N - 64 -back to the refrigerator. The liquid nitrogen storage tank is used, effectively, as a nitrogen condenser. VJR transfer lines must be used for the 80°K line from the refrigerator to the liquid nitrogen storage tank because the operating pressure of 150 psig is above the maximum operating pressure recommended by the manufacturer for the more economical VJSF transfer line. The cryogenerator is shown in greater detail in Figure 31. The system is based on a modified Brayton cycle, utilizing two expander turbines for the 80°K load and one turbine (and a stand-by) for the 20°K load. The system is capable of simultaneously providing 400 watts at 20°K and 6000 watts at 80°K. A comment is in order on the 400-watt capacity at 20°K. For the combined system the size and capacity of the major components is determined by the 80°K load. Further, it is desirable to utilize turbines with maximum accumulated experience. Because of these factors, it is possible to increase the capability at 20°K from the approximately 150-watt minimum required to 400 watts, with no additional equipment or added cost. The system consists of two sub-systems: the compressor sub-system and the cold box instrument panel sub-system. The compressor sub-system, as received, would consist of two skid-mounted compressors complete with fnte~and after-coolers, shutdown equipment, motor starter disconnect, etc. The compressors are slow speed, continuous duty, industrial process machines of non-lubricated design. Safety shutdowns will be provided for low crankcase oil pressure, high inter-stage or discharge gas temperature, and high cooling water temperature. The cold box instrument panel sub-system consists of a high vacuum insulated cold box, process heat exchangers, expansion turbines and associated controls and instruments, all mounted on a common skid. The cold box assembly consists of a vertically-mounted cylinder with removable top flange, to which expansion turbines and heat exchangers are attached. The gas-bearing turbo expanders are mounted in the top flange of the cold box so that the cold box need not be opened for turbine replace-ment. The 80°K load is handled by two expansion turbines. One turbine may be shut down for part-load operation. In the event of failure of either of the 80°K turbines, or in the 10.2.2 - 65 -event that the 80°K load exceeds capacity of the system, liquid nitrogen is automatically admitted to the heat exchanger to maintain the designated return gas temperature. Two 750 scfm compressors operate in parallel. For full load conditions about 1000 scfm is required. Under normal operating conditions the excess capacity will be by-passed back to compressor suction. In the event of failure of either of the compressors, the remaining compressor unit is sufficient to provide 400 watts at 20°K and 6000 watts at 100°K, or 6000 watts at 80°K with supplemental liquid nitrogen. A stand-by turbine is provided for the 20°K load. This unit will be started automatically in the event of failure of the operating unit. Start-up of the stand-by unit will require approximately two minutes. Any one turbine may be removed for service without interrupt-ing the operation of the remainder of the system. It is possible to remove a turbine from a cold system in approxi-mately 30 minutes. An auxiliary bearing gas supply is provided to ensure an adequate flow of bearing gas. An accumulator is provided to damp out fluctuations in the compressor discharge and to avoid loss of helium when the system is warmed up. Building requirements of the components of configurations V and VI are shown in Table XXI I. Dimensions shown in Table XXI I, for the cold box, are for a vertically-oriented unit with a flanged top. At no extra cost a horizontally-oriented cold box can be obtained which would be 96 in. H x 84 in. x 144 in. and require an equal floor area, in the long direction, for rolling out the internals. Instrumentation and Controls The refrigeration system will be purchased as a self-contained unit, complete with controls required for its operation. The control system will provide for manual start-up. It will be adequate for unattended operation, with automatic starting of stand-by components and an automatic shutdown in the event of component failure. Logic and control elements compatible with the central control system will be installed by the equipment supplier. Two surface temperature sensors will be installed on each 20°K and 80°K array. These may be of the platinum resistance type and should be installed with one sensor near the refrig-erant tubes and one unit on the extended surface, remote from the refrigerant tubes. Both sensors should be installed near the refrigerant exit end of the array. Accuracy of these temperature sensors should be ±0. 1°K. TABLE XX 11 BUILDING REQUIREMENTS OF COMPONENTS OF CONFIGURATIONS V AND VI Number Size Weight Component Required Location (each) (each) 1 b Integrated 20°K and 80°K Cryogenerator Compressor 2 Mechanical services 8811 H X 10111 X 8311 12,200 room + 4811 0 .H. Cold Box I Mechanical services 14411 H X 9611 X 9611 4,000 room + 14411 O.H. He accumulator I Outside building 4811 H X 20511 X 4011 3,500 LN2 Storage Tank 1 Outside building 28011 H x 10811 x 13211 empty (5,000 USga 1) (accessible by truck) + 3611 O.H. 24,000 fu 11 58,000 LN2 Circulating pump 2 At base of LN2 tank 3611 H X 1411 X 1611 300 + 3611 O.H. Power (each) hp 200 ---1.5 Coo Ii ng Water (each) USgpm 20 ----"' "' - 67 -10.2.3 Maintenance Requirements The maintenance requirements will, of course, be a function of the system selected. Maintenance of the liquid nitrogen storage tank will consist of tests of the safety relief vents, pressure regulators, etc. at annual intervals. Maintenance of the refrigerators proposed for nitrogen 1 iquefaction in configurations I, 111 and IV wi 11 include: Every 500 hours - a running check of safety devices and blow-off contaminants Every 1000 hours - shut down machine to clean up regenerator, coolers and strainers Every 5000 hours - shut down machine for oil change and check of safety devices and operating controls Maintenance of the 20°K refrigerator in configuration I will include shutting down every 500 hours for clean-up of regenerator and to check safety devices. During operation machine capacity decreases due to contamina-tion of the regenerator with oil. The manufacturer states that machine capacity decreases about 10% in 500 hours. It should be noted that a decrease of 10% in capacity will reduce the capacity to 42 watts - below the calculated thermal load of 46 watts at the end of one week's operation at design gas load. A decrease of 10% from the 11nominal 11 machine capacity of 60 watts will result in a capacity of 54 watts - above the calculated load of 46 watts. Thus, it may be necessary to clean up the rega,erator at intervals of less than 500 hours, depending upon the characteristics of the specific machines received by TRIUMF. Maintenance of the 2o~K refrigerator in configuratiors I I I and IV would be similar to the requirements of the integrated system in configurations V and VI. The turbine expander uses gas bearings and so, under normal operating conditions, has no wearing parts and no maintenance required. However, careful attention must be given to maintaining a stand-by supply of clean helium for bearing gas. It should be noted that the turbine expanders are more susceptible to damage during start-up and shutdown than during normal operation. Thus, the refrigerator would not normally be shut down except for maintenance. The normal control system dumps refrigeration 1nto a high temperature heat - 68 -exchanger in order to match machine output with required capacity. Thus, the machine may be operated for extended periods with zero net output. The compressors will require: Every 1000 hours - shut down compressors (in sequence) to change oil and check safety devices Every 5000 hours - warm up system to blow off con-taminants and check safety devices 10.2.4 Test Requirements The following tests should be run on the refrigerator as received from the supplier: 1) Check mechanical operation. 2) Check control system and safety devices. 3) Test refrigeration output. This may be accomplished by providing a small closed loop with flow characteristics reasonably approximating the operating loop and with an electric heater to provide a thermal load. Most faults, both of a mechanical nature and in the refrig-erator control system, will become evident early in the operating life of the unit. Thus, it is desirable that a few hundred hours of operation be accumu1ated before the system is required for cyclotron operation. This operating time may be accumulated using the test thermal load. 10.2.5 Operation and Performance Major performance parameters of the various configurations are shown in Table XXI I I. The major differences between the configurations are derived from the difference in capacity at 20°K and reliability. The times shown for average unscheduled outage are derived from a reliability analysis which considers possible malfunctions, the time required to correct the fault and the probable frequency of such a fault occurring. Un-scheduled outages caused by operator error and power interrup-tion are not included in Table XXI I I. Potential outages from the following are significant: 1) Mechanical failure of 20°K refrigerator 2) Simultaneous failure of both liquid nitrogen pumps 3) Non-delivery of liquid nitrogen by commercial supplier TABLE XX 111 PERFORMANCE OF REFRIGERATION SYSTEMS Configuration I II Net output at steady state: at 20°K w 471) at 80°K w 6,400 Time for cooldown, from warm, of 20°K h 0.5 refrigerator Time for cooldown, from warm, of 80°K h 0.3 refrigerator Time for cooldown, from warm, of 20°K h 2. 83) Not array and T.L. Time for cooldown, from warm, of 80°K h 0.8 feasible array and T.L. Time for cooldown, from 233°K (during h I. 83) regeneration), of 20°K array and T.L. Time for cooldown, from 233°K (during h 0.6 regeneration), of 80°K array and T.L. Average unscheduled outage 4) h/yr 48 Notes: I) Minimum net output guaranteed by manufacturers is: 47 W Nominal capacity is: 60 ± 12 W Capacity decreases about 10% in 500 h of operation 2) With LN2 precooling Without LN2 precooling, time is about 8 h 3) Both 20°K refrigerators operating Time is calculated on the basis of nominal capacity of 60 W II I 200 6,400 22) 0.3 0.6 0.8 0.4 0.6 34 4) Outage caused by operator error.and power interruption not included IV V 200 400 6,400 6,000 22) i2) 0.3 22) 0.8 0.3 0.8 0.8 0.5 0.2 0.6 0.6 34 33 VI 400 6,000 i2) 22) 0.4 0.8 0.2 0.6 33 0--1...0 _J - 70 -4) Failure of transfer lines by vacuum leak or gross mechanical damage 5) Failure of instruments and controls by malfunction or mechanical damage The average number of hours per year that the refrigeration systems will not function is shown in Table XXllland these averages are consistent with industrial areas such as chemical plants where significant emphasis is placed on re 1 i ab i 1 i ty. 10.2.6 Cost Estimates and Suppliers Estimates of capital and operating costs of the refrigeration equipment are shown in Tables XXIV and XXV. The cost break-down of the refrigerator for configurations V and VI is as fol lows: Basic unit Add for two compressors Add for stand-by 20°K turbine and automatic start helium accumulator, piping, freight, foundation Mi see 11 aneous TOTAL $136,000 10,900 19,300 18,800 $185,000 Data for specific machines have been used in the development of Tables XXIV and XXV, primarily because it is possible to assess more accurately the reliability of these existing machines. However, other groups are capable of and interested in developing cryogenerators of similar output. Thus, it is recommended that the selected cryogenerator(s) be purchased after firm bids have been received under a performance specification from selected suppliers. 10.3 Alternative Concepts Considered 10.3. 1 Cryogenerator Located in Vault The possibility of qenerating the 20°K refrigeration at the load, i.e. within the vault, has been considered. Such a system offers the following potential advantages: 1) Elimination of 20°K transfer lines and associated thermal load 2) Uniform temperature distribution along the 20°K array resulting from the use of a boiling fluid TABLE XXIV CAPITAL COST OF REFRIGERATION EQUIPMENT Configuration I 11 111 IV V VI Description - 20° Refrigerator Phi 1 i ps Phi 1 i ps Airco 11A11 Ai rco 11A11 Ai rco 11C11 Ai rco 11C11 PGH-105 PGH-105 80° Refrigerator Phi 1 i ps Phi 1 ips Phi 1 i ps Phi 1 i ps Ai rco 11C11 Ai rco 11C11 PPG-400 PPG-400 PPG-400 PPG-400 20°K Refrigerator $ 55,400 $11O,100 $110,100 $185,000 $185,000 Installation and Testing 6,100 9,900 9,900 11 , 200 11 , 200 Sub-Total 61,500 120,000 120,000 196,200 196,200 --..J 80°K Refrigerator 66,500 66,500 66,500 - -LN2 Tank 20,500 Not 20,500 20,500 21 , 700 21 , 700 LN2 Return Pump and T.L. 7,500 feasible 7,500 7,500 10,100 10,100 LN2 Circulating Pump and T.L. 20,500 20,500 20,500 19,100 19,100 Installation and Testing 11,900 11,900 11 , 900 6,400 6,400 Sub,..Total 126,900 126,900 126,900 57,300 57,300 T O T A L $188,400 $246,900 $246,900 $253,500 $253,500 TABLE XXV ANNUAL OPERATING COST OF REFRIGERATION EQUIPMENT Configuration I and I I 111 and IV 20°K 80°K 20°K 80°K Refr i g. Refr i g. Total Refr i g. Refri g. Total Technician $ 4,000 $ 5,000 $ 9,000 $ 4,000 $ 5,000 $ 9,000 Maintenance 4,000 8,500 12,500 5,500 8,500 14,000 Power at 0.5¢/kWh 1,000 4,400 5,400 2,200 4,400 6,600 Water at 2¢/Mgal 100 300 400 100 300 400 Consumables and 1,500 2,000 3,500 2,000 2,000 4,000 mi see 11 aneous T O T A L $10,600 $20,200 $30,800 $13,800 $20,200 $34,000 V and VI 20°K 80°K Refr i g. Refr i g. 20° K and 80° K Refrigerators Combined Total $ 6,000 12,700 9,900 300 3,000 $31,900 -...J N - 73 -3) Ability to operate each half of the array independently 4) Reliability derived from a multiplicity of refrigerators A technically feasible system is shown schematically in Figure 32. Refrigeration at 20°K is derived from a nitrogen-hydrogen cascade Joule-Thompson refrigeration cycle. Hydrogen at room temperature, piped from compressors located outside the vault area, is cooled to 80°K in heat exchangers against the liquid nitrogen and is then expanded through a Joule-Thompson valve for partial liquefaction. The following disadvantages are associated with the system: 1) Hazards associated with handling of high pressure hydrogen within the vault and mechanical services room 2) Difficulty of access to Joule-Thompson valves, heat ex-changers and other components located within the vault 3) Decreased confidence in the design of the 20°K array if designed for heat transfer to boiling hydrogen 4) Economics On the basis of these disadvantages the concept has been excluded. 10.3.2 Use of 20°K Refrigerator as a Helium Liquefier The possibility of using 11excess 11 refrigeration at 20°K to reliquefy helium for experimental purposes has been considered. The 20°K refrigerator associated with configuration I has no 11excess 11 capacity which could be used for the liquefaction of he 1 i um. The refrigerator associated with configurations V and VI has, at steady state, about 300 watts at 20°K which could be utilized for the liquefaction of helium. The required modi-fications for the Airco 11C11 machine are shown schematically in Figure 33. A separate compressor and separate passes in the heat exchangers are necessary to avoid mixing the clean helium in the cryopanel circuit with the 11dirty 11 helium to be liquefied. Because the normal control method for the machine dumps refrigeration into a high temperature heat exchanger to - 74 -regulate net output, addition of the helium liquefier would not affect turbine operation. Plugging of the liquefier section with contaminants would not interrupt turbine operation. The control system would satisfy the load requests of the 20°K array, then use ''excess" refrigeration for the liquefaction of helium. 300 watts available at 20°K would provide a helium liquefaction rate of about 15 litres/hour. Capital cost (equipment only) of the additional equipment shown in Figure 33 has been estimated at $42,000. For comparison, a separate helium refrigerator to produce 10 litres/hour without 1 iquid nitrogen precooling and 20 litres/hour with liquid nitrogen precooling costs about $60,000. Thus, utilizing "excess" refrigeration capacity at 20°K to liquefy helium for experimental purposes appears attractive if: 1) "excess" capacity at steady state approaching 300 watts at 20°K is available; and 2) the specific refrigerator selected is amenable to the addition of the required equipment. 10.3.3 Use of Liquid Nitrogen Machine The possibility of utilizing the 80°K refrigerator, in con-junction with an air separation column, to produce liquid nitrogen, rather than as a nitrogen reliquefier, has been considered. With the proposed configuration of refrigeration equipment, loss of nitrogen from the storage tank will occur whenever the pressure in the liquid nitrogen storage tank exceeds the set pressure of the relief vent. This will occur when the 80°K load exceeds the capacity of the refrigerator, for example, during cooldown of the 80°K array and transfer line. Nitrogen lost from the storage tank will be replaced by liquid nitrogen from a commercial supply. Use of a liquid nitrogen machine would allow refilling of the liquid nitrogen tank when refrigerator capacity exceeds the 80°K load. ' The following factors are significant: 1) Cooldown of the 80°K array and transfer lines requires about 450 litres of liquid nitrogen representing an operating cost of $27.00 at 6¢ per litre. Conversion of - 75 -the S0°K refrigerators to liquid nitrogen machines would cost in the order of $50,000. 2) Because the capacity at S0°K for the refrigerator con-figurations discussed closely matches the steady-state load, little "excess" capacity is available for refilling the storage tank. 3) Reliability of the 80°K refrigerator would decrease significantly as a result of the susceptibility to plug-ging when handling gas from an open system. Thus the use of•Jiquid nitrogen machines does not appear attractive. 10.3.4 Liquid Helium for Stand-by Refrigeration at 20°K The possibility of utilizing a liquid cryogen to "store" refrigeration at 20°K has been considered. Such a system offers the potential advantage of providing stand-by refrigera-tion to maintain operation of the 20°K array in the event of failure of the 20°K refrigerator(s). Only two candidate cryogens exist: liquid helium and liquid hydrogen. Liquid hydrogen has been excluded because it would be necessary to operate a liquid hydrogen system below atmospheric pressure to depress the boiling point below 20.3°~ and because of the inherent hazard associated with the handling of liquid hydrogen. A technically feasible system utilizing liquid helium is shown schematically in Figure 34. In the event of operating failure of the 20°K refrigerator(s), the transfer lines to the refrigerator are isolated and helium circulated through a cold fan and heat exchanger. Refrigeration is derived from liquid helium circulated from a storage tank through the heat exchanger and discharged to the atmosphere. It would not be economically feasible to compress or otherwise capture more than a fraction of the helium vapourized. Liquid helium con-sumption, for a net load of 50 watts at 20°K, would be about 25 litres/hour. The system is, of course, inefficient as helium is discharged to the atmosphere at about 23°K. Storage of 2,000 litres of liquid helium would be required to provide 50 watts net at 20°K for a period of 72 hours. Boil-off losses from such a tank would cost $51,000 per year at $3.50 per litre. Thus, the scheme would be attractive only if a helium liquefier is available to reliquefy the boil-off from the storage tank. The helium liquefier utilizing "excess" capacity at 20°K, discussed under Section 10.3.2, could be - 76 -used to liquefy the boil-off from the liquid helium storage tank. Capital cost of the equipment shown in Figure 34 has been estimated at approximately $60,000. This relatively high capital cost, for stand-by capacity of only 72 hours, indi-cates that reliability could more effectively be improved by the addition of redundant equipment to the refrigeration system. However, this conclusion should be reviewed in the event that helium liquefaction capacity is added to the 20°K refrigerator. 10.4 Auxiliary Diffusion Pump System Because hydrogen is a significant component of the design gas load and is not pumped by the cryopanels, an auxiliary pumping method is required to pump this mass 2 fraction. A system of eight 10 in. (nominal) diffusion pumps has been specified to perform this function. The auxiliary diffusion pump system will also be used during the pumpdown period and bakeout of the resonators. A schematic diagram of the auxiliary diffusion pump system is shown in Figure 35. 10.4.1 Description of Stack Components The requirements for the diffusion pumps are similar to those of the 32 in. diffusion pump system (see Section 9, l. 1). Diffusion Pump Traps Diffusion pump traps will be of the double-bounce type with water baffle and liquid nitrogen baffle in combination. The liquid nitrogen baffle is of the circulating type in order to reduce the time required for regeneration and to be consistent with the sub-cooled liquid nitrogen system. Isolation Valves Isolation valves will be air operated and must be capable of throttling and slow opening as well as rapid closing in case of system upset. Commercially available valves have a closing time of 2 to 5 seconds. Because of the severe radia-tion environment, valves must use metallic seals throughout, except on the main gate seal where the use of an elastomer is permissible. This requirement .also applies to seals in the actuator, i.e. piston sealing 0-rings, etc. The gate seal is replaced by dropping the stack and removing the valve from the stack; the valve disc is then removed through the back of the valve and the seal replaced. Backing System Backing requirements of the auxiliary diffusion pump system are satisfied by a single 150 cfm rotary oil seal pump. This No. Reqd. 8 1 - 77 -pump is identical to the rotary pumps used in the roughing system (see Section 8. 1. 1) which provide an effective back-up system in case of failure of any one unit. The backing line will be 4 in. diam stainless steel pipe. Backing pump exhaust will be fed into the air disposal system. Refrigeration for Diffusion Pump Cold Traps The cold traps of the auxiliary diffusion pumps will obtain refrigeration from a closed cycle sub-cooled liquid nitrogen system. The required lines and fittings are shown schematical-ly in Figure 36. The distribution line consists of semi-flexible transfer line, modified for the radiation environment. The total length of the distribution header is approximately 170 ft. Each trap is provided with a remotely operated valve so that operation of each stack may be independently controlled. Each stack is also equipped with a manual valve to permit removal of any one stack without interrupting the operation of the remaining stacks. The distribution line is provided with a balance valve so that the pressure drop through the header can be adjusted to match the pressure drop through the 80°K panels. Building Requirements Space requirements of the auxiliary diffusion pump system are listed in Table XXVI. Equipment TABLE XXVI BUILDING REQUIREMENTS OF AUXILIARY DIFFUSION PUMP SYSTEM Size Weight Location each • each Diffusion pump Vault See 750 lb stacks Fig.39 Backing pump Mechanical 4411 H X 950 lb Services 2511 X Room 2411 Power Water each each 4.5 kW l .5 gpm 7,5 hp 1 gpm - 78 -10.4.2 Instrumentation and Controls Each diffusion pump stack will be controlled in a similar manner to that described in Section 9.2 for the 32 in. diffusion pump system. In the case of failure of the backing pump, one of the rough-ing system rotary pumps will be started and cut into the system. Each diffusion pump is fitted with a manually controlled valve on the foreline so that any diffusion pump can be removed for servicing without interrupting the operation of the remaining pumps. Control system procedures in case of emergency are listed in Table XXVI I. 10.4.3 Maintenance Requirements Normal maintenance of the diffusion pump stacks will consist of replacement of burned-out heaters, changing pumping fluid and replacement of valve gate seal. This work will normally be performed outside the vault by removing the stack as a unit. The diffusion pumps are fitted with cartridge-type heaters which are replaceable from the outside with pump installed. This can be done during the regular maintenance periods, since the pump will function with one heater burned out. Diffusion pump oil should not require changing more frequently than once a year, and viton valve gate seals should not require replacement more frequently than once in six months, as explained previously in Section 9,3. Maintenance of the backing pump will include changing lubri-cating oil every 1000 hours, or as required by contamination. Shaft seals and V-belts will require replacement at about 10,000-hour intervals. 10.4.4. Test Requirements The test requirements are similar to those of the 32 in. diffusion pump system (see Section 9.4). 10.4.5 Operation and Performance The auxiliary diffusion pumps will be throttled into the system when chamber pressure reaches 2 x 10- 2 Torr and will be fully open at chamber pressures of 1 x 10- 3 Torr. The diffusion pumps will operate during the bake, with temperature rise con-trolled so that the stack pressure does not exceed 10- 3 Torr. - 79 -TABLE XXVI EMERGENCY PROCEDURES AUXILIARY DIFFUSION PUMP SYSTEM 1. Pressure at throat of diffusion pump exceeds 2 x 10-2 Torr 2. Failure of backing pump 3. Failure of electrical power (assuming do not lose instru-ment air) 4. Failure of cooling water on diffusion pump stack 5. Failure of LN2 supply 6. Failure of instrument air supply - Close isolation valves Switch to rotary pump in roughing system - Close isolation valves (control valve is normally open, energized to close) Switch to potable water supply If flow not restored, turn off diffusion pumps, close isolation valves and cool boilers - Close isolation valve Shut down diffusion pump Cool diffusion pump boilers Switch to emergency air supply - Close diffusion pump isolation valves Shut down diffusion pumps - 80 -Pumpdown performance is shown in Figure 4. A pressure of 6 x 10- 8 Torr (SCS) is reached in 15 hours pumping time, based on the design gas loads. Pumping speeds of the diffusion pump stack selected are: mass 2 mass 18 mass 28 mass 44 3200 litres/sec 4150 litres/sec 1000 litres/sec 2200 litres/sec The auxiliary diffusion pumps are also utilized during cryo-panel regeneration. After beam shutdown the refrigerator is isolated and the panels allowed to warm to 233°K. Analysis has shown that the rate of desorption of gas from the cryopump can be readily handled by the auxiliary diffusion pump system. When chamber pressure has been reduced to about 10-s Torr, the isolation valves are closed in sequence, the diffusion pump boiler cooled and the cold trap regenerated. This procedure avoids the necessity of programming the trap temperature to prevent flooding the diffusion pump. Baking the trap and isolation valve to 125°C is a worthwhile step. The diffusion pump is then restarted, the liquid nitrogen trap cooled down and put back into operation before the isolation valve is reopened. Cooling of the cryopanels completes the regeneration sequence. During normal operation oil backstreaming from the diffusion pumps can be as high as l x 10- 7 g/min, depending on trap design. Gross air inrush due to operator error will cause massive oil backstreaming, an event which is predicted to occur twice in the first year and once every year thereafter. This frequency would not significantly be reduced by additional instrumenta-tion. The closing time of 2 seconds for commercially available valves is too slow to prevent massive oil backstream-ing in case of accidental air inrush. To reduce the closure time significantly would require the use of a special fast valve. The auxiliary diffusion pumps will remain open to the chamber during normal operation. However, after weeks of operation reduction of gas loads should permit shutdown of one or more stacks on each side of the chamber. This procedure will reduce the quantity of oil reaching the chamber by backstreaming. 10.4.6 Cost Estimates and Suppliers Estimated capital cost of the auxiliary diffusion pump system is presented below: Diffusion pumps Traps Valves Backing pump - 81 -LN2 T.L. and fittings Mi see 11 aneous Installation and testing TOTAL @ @ @ $2,400 3,260 2,910 $19,200 26,100 22,500 2,280 7,900 19,300 4,600 $101 ,600 Capital costs are based on a VAT (Vat Aktiengesellschaft) swing disc valve, available from High Voltage Engineering, combined with a trap and diffusion pump supplied by Whittaker Corporation. The valve is stainless steel construction, has a bellows sealed actuator, and has no body seal. However, the entire diffusion pump stack must be removed to replace the main valve disc seal. If in-line servicing is desirable, a valve which conforms to specifications and permits in-line servicing is available from Whittaker Corporation.at an addi-tional cost of approximately $2,500 per valve, or $20,000 total. Cost estimates are based on aluminum foil metal seals between all flanges. Annual operating costs of the auxiliary diffusion pump system a re as fo 11 ows : Technician Maintenance Power and water Consumables and miscellaneous TOTAL 10.5 Cost Estimates for Cryopumped Systems $1 ,200 900 I ,825 700 $4,625 Estimated capital and annual operating costs of cryopumped systems are shown in Tables XXVI I and XXIX. Estimates for capital cost include installation, testing and engineering. Estimates for operat-ing costs include amortization calculated on a 10-year straight line basis. - 82 -TABLE XXV I I I CAPITAL COST OF CRYOPUMPED SYSTEMS Configuration I 11 111 IV V VI Descrietion Cryol i ne Flat Cryo 1 i ne Flat Cryol i ne Flat Array Shield Shield Shield 20°K T. L. VJLNS VJLNS VJMLI VJMLI VJMLI VJMLI 80°K T. L. SFX SFX SFX SFX SFX SFX Array $ 73,800 $ 73,800 $ 65,100 $ 73,800 $ 65,100 20°K T. L. 40,000 25,500 25,500 25,500 25,500 80°K T. L. 23,600. 23,600 23,600 23,600 23,600 20°K Refrigerator 6 l ,500 120,000 120,000 196,200 196,200 80°K Refrigerator 126,900 Not 126,900 126,900 57,300 57,300 Ro.ugh ing Sys tern 31 , 300 Feasible 31,300 31 , 300 31,300 31,300 Aux. D.P. System 101,600 101,600 101,600 101,600 101,600 Gauging 2,500 2,500 2,500 2,500 2,500 Dry Air Source 4,300 4,300 . 4,300 4,300 4,300 Test Equipment 10,000 10,000 10,000 10,000 10,000 Engineering 68,000 63,000 63,000 53,000 53,000 T O T A L $543,500 $582,500 $573,800 $579,100 $570,400 TABLE XXIX ANNUAL OPERATING COST OF CRYOPUMPED SYSTEMS Configuration I 11 111 IV Arr~y - - -S0°K and S0°K T.L. 900 900 900 S0°K Refrigerator 10,600 13,SOO 13,SOO S0°K Refrigerator 20,200 20,200 20,200 Not Roughing System 1,100 feasible l, 100 l, l 00 Aux. D.P. System and Associated equipment 5,300 5,300 5,300 LN2 Consumed at 6¢/1 itre S,300 S,300 l l ,000 Sub-Total 46,400 49,600 52,300 Amortization 54,300 5S,200 57,400 (10 year straight line) T O T A L $100,700 $107,SOO $109,700 V -500 31,900 -l, 100 5,300 6,Soo 45,600 57,900 $103,500 VI -500 31,900 -1,100 5,300 7,500 46,300 57,000 $103,300 00 w - 84 -11. MAIN CHAMBER GAUGING Monitoring of chamber pressure during pumpdown in the cyclotron "magnet-off" condition can be accomplished using diaphragm, thermo-couple and cold cathode ion gauges to cover the range from atmospheric pressure to below 10- 8 Torr. The cold cathode discharge gauge is a rugged design which is not damaged by pressure bursts or accidental exposure to air. The General Electric Co. Trigger gauge operates over a wide range, 10- 4 to 10- 14 Torr. The small magnet, length l .5 in., l ,9 in. o.d., l .2 in. i .d., will have negligible effect on the beam characteristics when placed more than 10 in. from the median plane. Cycling of the cyclotron magnet will cause hysteresis effects in the permanent magnet of the gauge. Stability will be achieved after a few cycles, and then the gauges will need to be recalibrated on a separate gauge calibration system. An increase in the magnetic field for a cold cathode gauge merely increases the gauge sensitivity. (For hot cathode gauges, however, the presence of a magnetic field causes oscillation problems of the filament when AC operated and a mechanical strain on the filament when DC operated.) It is recommended that a second identical set of cold cathode gauges be used for the "magnet-on" condition. After magnet stabilization and recalibration as described above, a correction curve for gauge readings in the "magnet-off" and "magnet-on" condition is a simple final calibration procedure. By using two separate gauge systems, redundancy is obtained, provided that gauges in the two systems are interchangeable. Locations for gauges have been determined by the TRIUMF magnet group where the vertical component of field B is less than l .5 kG, uniform to better than 10%, and the transverse fields BR and B8 are less than 10% of B2 . The optimum positions are close to the vacuum chamber and the valley centre line, and at machine radii less than 190 in. SLAC14 have developed a gauge control unit for the G.E. Trigger gauge with fast response features for activation of safety control devices. It is recommended that both the gauge and control unit be tested by TRIUMF on the centre region model. The importance of correct analysis of the residual gas composition was shown in Section 4 and Table I I I, where the stripping cross-section pressure p3 of 6.4 x 10-8 Torr meets criterion 2.2, but the total gas pressure is only 1.7 x 10- 7 Torr. Since 65% of this total pressure is due to hydrogen and the sensitivity of cold cathode gauges is particularly low for hydrogen compared to other gases, the reading of the total pressure gauge can be seriously misinterpreted unless an analysis of the gas composition is made. Analysis in the "magnet-off" condition is no problem, but a satisfactory technique for use in the "magnet-on" condition which does not require magnetic shielding of commercial instruments has not yet been found. It would be desirable but not mandatory to develop a method of analysis for the "magnet-on" condition. - 85 -12. DRY GAS SOURCE It is desirable to provide a source of dry gas for venting the chamber to atmospheric pressure. Backfilling the chamber with dry gas will reduce the sorption of water on chamber surfaces and thus reduce the time required for subsequent evacuation. The dry gas source system should be capable of supplying the required 3200 scf of dry gas in about one hour and of continuing to provide a few cfm to maintain the chamber at a slight positive pressure to avoid "breathing" due to fluctuations in barometric pressure. Two alternatives have been considered: dry nitrogen and dry air. Dry nitrogen could readily be obtained by vaporizing 1 iquid nitrogen from the storage tank by means of an ambient air heat exchanger. Altern-atively, a desiccant system may be used to reduce the moisture content of ambient air, which is then piped to the chamber. The use of dry nitrogen is attractive from an economic point of view but presents a significant hazard in the form of potential oxygen deficiency. Safety considerations would dictate that the dry nitrogen system not be used on occasions when the chamber is opened for personnel to work inside the chamber. Further, a significant hazard would exist when the chamber is vented and an opening into the chamber is created by the removal of feed-throughs, etc. Under these conditions, nitrogen will flow out of the opening and produce an oxygen-deficient area near the opening. Normal oxygen content of the atmosphere is approximately 21%. Below 16% oxygen few working men are free of the symptoms of oxygen deficiency. Minor symptoms, such as headaches and fatigue, quickly develop into the more serious symptoms of loss of muscular co-ordina-tion, fainting, unconsciousness and death. The symptoms are usually difficult for the affected person to recognize, as the lack of oxygen affects the ability to reason. The affected person will often con-tinue to perform non-essential tasks rather than move to an escape area. Because of the radiation environment in the vault a minimum number of staff wi 11 enter this area. The 11buddy system", the use of 1 ife lines, and other safety precautions required for working in a poten-tially oxygen-deficient atmosphere represent a severe limitation. Thus, the use of dry nitrogen has been excluded because of the associated hazard to personnel. Dry air may be obtained from a desiccant system, such as that shown in Figure 38. The absorption capacity of molecular sieves is a strong function of operating pressure, so the compressor is provided to reduce the required quantity of desiccant. The compressor is a standard, tank-mounted, lubricated unit. The oil filter protects the desiccant from oil vapour discharged from the compressor. The dryer - 86 -is a molecular sieve unit with electric regeneration. Regeneration will be required after each use and will require about eight hours. The after-filter is provided to prevent desiccant being carried into the chamber. The system will provide the required 3200 scf of air to vent the chamber at a dew-point of -70°F (15 ppm by weight) in one hour. The quantity of desiccant required is established by the quantity of air to be dried rather than the effluent dew-point, so that raising the effluent dew-point would not significantly reduce the cost of the unit. After venting to atmospheric pressure, about 5 cfm may be supplied by the instrument air source to maintain the chamber at a slight positive pressure. In addition to its primary function, the dry air source could act as a back-up to the instrument air source. Space requirements of the dry air source are: Size Location Weight Power Coo 1 i ng water 8411 H x 2911 x 11011 Mechanical services room 1600 lb 10 hp motor on compressor 5 kW heater for regeneration 2 US gpm Estimated capital cost of the dry air source is $4,300; the cost breakdown is shown below: Compressor Oil filter, dryer, after-filter Piping and controls Mi see 11 aneous Installation and testing TOTAL $2,300 700 700 200 400 $4,300 - 87 -l 3. LEAK TEST I NG 13. 1 Leak Testing Requirements The req~irements of the leak testing procedure are: 1) to establish, with a high degree of confidence, that the actual leak rate is less than the allowable leak rate, and 2) to minimize delays in the construction schedule, especially the time required for leak testing of the assembled chamber in situ. The maximum a 1 lowab le leak rate has been established as follows: Maximum total leak rate = 8 X 10-6 Torr 1 itre/sec (air) = 3 X 10-s atm cm3/sec (he 1 i um) Maximum single leak = l X 10- 1 Torr 1 itre/sec (air) = 4 X 10-7 atm cm3/sec (helium) It is an additional requirement of the leak-testing procedures that sufficiently sensitive techniques be available to locate leaks to permit pumpdown from atmospheric pressure. For these circumstances the allowable leak rate may be conservatively estimated at 1% of the throughput of the pumping system. This requirement is shown, as a function of chamber pressure, for the cryopumped system in Fi~ure 39, The requirements of the diffusion pumped system during pumpdown are less stringent by about one order of magnitude in the pressure range where the diffusion pumps are operating. 13.2 General Leak Testing Procedure All components of the cyclotron which represent a potential leak should be leak tested as soon as received, to provide maximum time for repair or replacement. This preliminary test should be performed on such elements as the resonators, electrical and mechanical feed-throughs and mechanical actuators as well as components of the vacuum pumping system. Components such as vacuum valves, diffusion pumps, etc. will be purchased under a specification which includes a requirement for leak testing by the supplier. Leak testing of these components by TRIUMF will be of a confirming nature, prior to acceptance of the equipment. It may be desirable, for reasons of economics and delivery, to purchase components such as interconnecting vacuum piping, coolant piping for the resonators and perhaps the chamber itself from suppliers not equipped to perform leak tests of the required sensitivity. Specifications for these components should, in general, require that the equipment successfully pass a leak test, to a quantitative speci-fication, before acceptance by TRIUMF. - 88 -As soon as all components in an assembly are received, and storage space is available, the components should be made up into an assembly and the assembly leak tested. The vacuum chamber for the centre. region model could be very usefully employed in the leak testing of components and assemblies. The cyclotron vacuum chamber will be assembled and leak tested in an experimental area, prior to installation in the vault. It wi 11 be necessary, of course, that all penetrations be blanked off for these tests. It is desirable that as many feedthroughs, etc. as possible are actually installed prior to these tests. Final leak testing will be performed as part of the commissioning procedure with the chamber in situ. 13.3 Leak Testing Techniques A sequence of leak-testing techniques will be used which will, in general, progress from simple, easily-performed tests of low sensi-tivity to tests of high sensitivity and a very high degree of confidence. When leaks are detected, it will be necessary to use probing techniques to locate the leak. However, the final test in each sequence should be an "inclusive" test to provide a high degree of confidence that no leaks exist larger than the sensitivity of the test system. A quantitative approach should be used in leak testing to ensure that a test of adequate sensitivity is being used and, conversely, to avoid wasting time by using a technique that is more sensitive than necessary. Because the sensitivity of a specific leak test is often a strong function of the test set-up (and not simply the leak detector used), the sensitivity of every set-up should be checked empirically. Either commercially available or laboratory prepared "calibrated leaks" may be used. For tests involving helium, or other tracer gas, it is good practice to introduce the calibrated leak to the system after the test has been performed to avoid raising the background during the test. Introducing the calibrated leak after a 11success-ful 11 test (i.e. no signal) will increase confidence in the (negative) result by demonstrating that a leak equal to the calibrated leak would very probably have been detected had it been present. Leak-testing techniques involving 1 iquids are not desirable as the liquids may (temporarily) plug leaks well above the requirements of the TRIUMF chamber. Leak testing must be performed in a controlled, organized manner with, for example, a specific program established, written records maintained and a marking system used to identify components that have been tested. - 89 -13.3. l Equipment Required The following equipment will be required for leak testing: 1 only ultrasonic translator detector Hewlett-Packard model 4916, or equal Minimum detectable leak, l x 10- 1 atm cm3/sec l only helium mass spectrometer leak detector Consolidated Electrodynamics Corp. model 24-120B, or equal Sensitivity, l part He in 107 parts air Minimum detectable leak, 5 x 10- 10 atm cm3/sec (time constant= 1 sec) Pumping speed 10 1 it res/sec at inlet flange Helium gas, plastic film, and miscellaneous supplies 13.3.2 Sequence of Leak Tests The sensitivity of various specific leak detection techniques applicable to the TRIUMF chamber and pumping system are shown in Figure 39. The following general sequence of leak tests will be performed on the assembled chamber and pumping system in the experimental area and/or in situ: l) Ultrasonic leak detection 2) Dynamic helium mass spectrometer (H.M.S.) test with roughing system operating 3) Dynamic helium mass spectrometer (H.M.S.) test with diffusion pumps operating 4) Selective bagging, probing and other techniques to locate specific leaks Commercially available ultrasonic leak detectors have, opti-mistically, a minimum detectable leak of 1 x 10- 1 atm cm3/sec when applied to vacuum systems. Application of a high quality ultrasonic leak detector should, with no difficulty, enable leaks to be found such that the total leak rate can be reduced to the point where the blowers of the roughing system can be started. Toward the lower end of the operating pressure of the blowers (i.e. micron range) ultrasonic techniques will be marginal in detecting leaks large enough to prevent further - 90 -pressure reduction. In this pressure range an alternate test is available in the form of a dynamic helium mass spectrometer test using the arrangement shown in Figure 40. However, the utility of this test is drastically limited by the response time of about 2000 seconds for 63% concen-tration. The long response time will make the test awkward and time consuming to perform, making it necessary to flush the system with air after each signal in order to reduce the background. The sensitivity of the test, for a response time of 10 seconds, has been plotted in Figure 39, In the low micron pressure region attainable by the rough-ing system, a static helium mass spectrometer test may be performed using the configuration shown in Figure 41. The long response time associated with this test makes it unsuitable for the location of leaks. However, it is an inclusive test and so can be performed with a high degree of confidence in the (negative) result. It is feasible to perform the test with a waiting time of 24 hours, which will provide a sensitivity below the allowable maximum total leak rate and maximum allowable single leak. Thus, it is possible to establish, prior to the installation of the diffusion pumps, that the chamber and appurtenances conform to the leak rate specific~tions. When the diffusion pumps are operating, a dynamic helium mass spectrometer test using the configuration shown in Figure 42 is possible. At chamber pressures below about 10- 4 Torr this test provides adequate sensitivity to estab-lish that the chamber and appurtenances conform to the leak r~te specification. These pressures are attainable in an unbaked (but clean) chamber. This technique is inclusive and is amenable to empirical calibration, and so provides a high degree of reliability in a successful (no signal) test. Selective bagging may be used to locate leaks that have been detected. The elastomer seal on the main chamber represents a special problem in leak testing. Techniques involving helium as a tracer gas are not generally applicable, depending on the size of the leak, because helium permeation through the elastomer will mask real leaks. 13.4 Comments on Leak Testing Leak-testing methods with adequate sensitivity are available to establish that the chamber and appurtenances conform to the leak rate specification and to perform initial chamber pumpdown. Very careful design, construction and installation of the chamber and internal components will be necessary to control virtual leaks. - 91 -Leak testing is by nature a tedious, frustrating task which must be performed with care and diligence. The TRIUMF chamber will include several hundred joints, connections and penetrations, all of which must be effectively leak-tight. • This objective is feasible but will not be easily accomplished. - 92 -14. CONSTRUCTION SCHEDULE It is desirable that the construction schedule be arranged to provide for: 1) Testing of all components prior to installation. Components should be tested as soon as received to provide maximum time for repair or replacement. 2) Testing of assembled chamber and diffusion pumping system prior to installation in situ. The combined meson and neutron area would be suitable for this test work. It is possible, but very awkward, to leak test the chamber with only the roughing system operable. It is desirable to install and test the diffusion pump stacks during this test sequence. For the cryopumped systems it would be possible, but awkward, to install and operate the refrigerator and arrays. If it would be necessary to subsequently remove the cryoarrays for the installation of the chamber in situ, they need not be installed for this test sequence, provided that prior tests have established a high degree of confidence in leak tightness. Estimated elapsed times for activities associated with the vacuum pumping system are shown in Table XXX. These activities may not be performed simultaneously, and it may not be possible to perform them consecutively because of restraints introduced by other activities. The elapsed times shown in Table XXX assume that the cryoarray will be installed during final assembly, but not during the test sequence performed in the experimental area. - 93 -TABLE XXX CONSTRUCTION SCHEDULE Elapsed Time - Weeks Establish final design gas load Engineering design and preparation of purchase specifications Request proposals, receive and evaluate proposals and award contracts Equipment and material delivery Testing of components Testing of chamber and diffusion pumping system in experimental area (Assembly and disassembly of chamber not included) Testing of chamber and pumping system in situ (Assembly of chamber not included) Cryosystem N/A 18 8 27 20 8 11 D.P. System N/A 16 8 23 19 9 9 - 94 -15. COMPARISON OF CRYOPUMPED AND DIFFUSION PUMPED SYSTEMS Significant features of the cryopumped and diffusion pumped systems have been summarized in Table XXXI. The following observations are pertinent: 1) Capital cost of the diffusion pumped system is significantly lower than any of the cryopumped alternatives. 2) Operating costs range from $46,400 to $52,300 per year with cryopumped configurations both higher and lower than the diffu-sion pumped system. 3) The higher pumping speed for mass 18 and mass 28 of the cryo-pumped system produces, for the design gas load composition, a SCS pressure lower by about a factor of 3 than the diffusion pumped system. 4) Required SCS pressure for design gas load is reached, effective-ly, as soon as the cryoarrays reach operating temperature (15 hours after start of pumpdown). Projectioris of decay of design gas load indicate that the diffusion pumped system will reach required SCS pressure about 100 hours after start of pumpdown. 5) Estimated non-operating time is about equal for all alternatives shown, but for the diffusion pumped system is a strong function of pumpdown time. 6) The cryopumping components are not vulnerable to gross air in-rush or operator error. The diffusion pump components of both systems are vulnerable to gross air inrush and operator error. 7) Massive oil backstreaming is predicted to occur occasionally for both systems. However, it is likely to be more serious for the 32 in. diffusion pump system. 8) The higher pumping speed for mass 18 of the cryopumped systems may achieve the required SCS pressure by baking of the resonators only. 9) The 10 in. diffusion pump stacks associated with the cryopumped system can be incorporated in the chamber without deletion of tie rods. 10) Final installation and testing of the cryopumped system would require about 2 weeks longer than for the diffusion pumped system. II) The 32 in. diffusion pumped system not only complicates the positioning of tie rods but also makes the trim coil fabrica-tion and installation much more difficult and costly. TABLE XXXI COMPARISON OF CRYOPUMPED AND DIFFUSION PUMPED SYSTEMS C n op umped Sys tern I 111 IV V DESCRIPTION Array Cryol ine Cryo 1 i ne Flat Shield C ryol i ne 20°K T.L. VJLNS VJMLI VJMLI VJMLI 80°K T. L. SFX SFX SFX SFX No. & size of diffusion pumps 8-10 11 8-10 11 8-10 11 8-10 11 20°K Load w 46 98 106 98 80°K Load w 6,040 6,030 6,660 5,380 20°K Cryogenerator 2-Phil ips Ai rco 11A11 Ai rco 11A11 Ai rco 11C11 PGH-105 80°K Cryogenerator 2-Phil ips 2-Philips 2-Phi 1 ips Ai rco 11C11 PPG-400 PPG-400 PPG-400 COST Capital Cost $ 543,500 582,500 573,800 579,100 Operating Cost $/yr 46,400 49,600 52,300 45,600 VI Flat Shield VJMLI SFX 8-10 11 106 6,010 Airco 11C'1 Airco 11C11 570,400 46,300 Diffusion Pumped System D.P. Cold Trap None SFX 6-3211 -2,200 None Commerc ia 1 LN2 Supply 408,900 47,800 \.D V, COMPARISON OF CRYOPUMPED AND DIFFUSION PUMPED SYSTEMS (cont) PERFORMANCE Pumping Speed mass= 2 mass= 18 mass= 28 1 it re 2 /sec litre /sec litre/sec Total pressure when full pumping speed attained Torr (design gas load) 12,800 1,025,000 70,500 1.]xl0-7 SCS pressure, 15 h after start of pump-down (design gas load) Torr I 6.4x10-s Time to reach 7xlo-s Torr, SCS (pressure) Time required for regeneration Non Operating Time h h Due pumpdown (3/yr) h/yr Due regeneration(34/yr)h/yr Due unscheduled outage h/yr 17 7.7 50 262 48 Total h/yr I 360 Oil Backstreaming at Steady State g/min I lxl0-7 II I 12,800 1,025,000 70,500 1. 7xl0-7 6.4x10- 8 14 6.3 43 214 34 291 lxl0-7 Cryop~mpe_<!_ System IV 12,800 840,000 74,500 l. 7xlo-7 6.4x10-B 15 6.4 44 218 34 296 l xl0-7 V 12,800 1 ,0?.5,000 70,500 l. 7xl0-7 6.4xl0- 8 14 6.1 42 208 33 283 l xl0-7 VI 12,800 840,000 74,500 l.7xl0-7 6.4x10-s 14 6.1 42 208 33 283 l xl0-7 Diffusion Pumped System 66,900 l l 4,000 26,700 2. 7xl0- 7 l. 9xl0-7 102 306 24 330 2xl0-6 I.O 0--COMPARISON OF CRYOPUMPED AND DIFFUSION PUMPED SYSTEMS (cont) Cryopumped System I 111 IV V VI OPERATION Vulnerable To: Gross Air Inrush . . . . Yes, produces oil contamination from D.P. 1s . . . Operator Error . . . Yes, produces oil contamination from D.P. 1 s . . . Power Interruption . . . . No. Valves on D.P.'s close . . . . . . . . . . . Must chamber be baked to reach operation pressure . . . . . . . . . . . . . . . No . . . . . . . . . . . with design gas load in 15 h7 Must resonator be baked to reach operation pressure . . . . . . . . . . . . . . . Yes . . . . . . . . . . . . with design gas load in 15 h7 CONSTRUCTION Must tie rods be omitted to accommodate D.P. 's7 . . . . . . . . . . . . . . No . . . . . . . . . . . . . Elapsed Time for: Testing in Experimental Area weeks . . . . . . . . . . . . . . 8 . . . . . . . . . . . . . Testing in situ weeks . . . . . . . . . . . . . . . 11 . . . . . . . . . . . . I I I I . . . . . . . . . . . . . . . . . . . . . . . Diffusion Pumped System Yes, oi 1 con-tamination Yes, oil con-tamination No Yes Yes Yes 9 9 \.0 ....... - 98 -16. RECOMMENDATIONS 1) The marginal 2O°K refrigerator capacity of configuration I results in disadvantages which outweigh the savings in capital cost. Thus, it is recommended that configuration I be excluded from further consideration. 2) The separate 2O°K and 8O°K refrigeration systems of configurations I I I and IV require more building space and result in higher capital and operating costs without signif-icant compensating advantages. Thus, it is recommended that configurations I I I and IV be excluded from further consideration. 3) Configurations V and VI differ only in the cryopump configu-ration. The lower 8O°K load associated with the cryoline would provide a desirable reserve capacity, but the greater space required in the cyclotron by the cryoline may be a significant limit, with the net result of perhaps a marginal preference for the cryoline configuration. However, the choice between array concepts should evolve clearly in the early stages of engineering if the cryopumped system is adopted. 4) The higher pumping speed of the cryopumped system (configura-tions V and VI) compared to the diffusion pumped system offers significant operating advantages. Thus, the cryopumped system is recommended if the higher capital cost is not pro-hibitive. - 99 -ACKNOWLEDGEMENTS The authors wish to express their appreciation to Mr. N. Milleron of the Lawrence Radiation Laboratory, Berkeley, for his interest and numerous suggestions throughout the course of this study. For their continuing interest in the vacuum pumping system design of the cyclotron, the authors wish to thank Dr. J.P. Hobson of the National Research· Council, Ottawa, and Dr. G. Lewin of the Plasma Physics Laboratory, Princeton. - 100 -REFERENCES 1. V.J. Harwood, TRIUMF Engineering Note TRI-EN-68-28 (1968) 2. M.K. Craddock, "Present Knowledge of the H- Gas Stripping Cross-Section", TRI-PN-68-2 (1968) 3. R.S. Barton and R.P. Govier, "Some Observations on the Out-gassing of Stainless Steel Following Different Methods of Cleaning", UKAEA Report CLM-R93 (1968) 4. E. Hoyt, "Effect of Surface Treatment and Baking on the Out-gassing Characteristics of 304 Stainless Steel Pipe", SLAC-TN-64-5 (1964) 5, Y.E. Strausser, "The Effect of Surface Treatment on the Out-gassing Rate of 304 Stainless Steel", Trans. 4th Inter. Cong. Vac. Tech. (1968) 6. Y.E. Strausser, "Review of Outgassing Results", Varian Associates VR-51 (1969) 7. G. Lewin, "Fundamentals of Vacuum Science and Technology", McGraw-Hill Book Company (1965) 8. O.K. Fredriksson, William M. Brobeck & Associates, Berkeley, California, private communication 9, K.L. McHugh, Monsanto Co., St. Louis, Missouri, private communication 10. R.W. King, N.J. Broadway and S. Palinchak, "The Effect of Nuclear Radiation on Elastomeric and Plastic Components and Materials", REIC Report No.~. 12 (1961) 11. R.L. Merriam and R. Viskanta, "Radiation Characteristics of Cryodeposits for Room Temperature Black Body Radiation", Adv. in Cryogenic Eng. J..i, (1968) 12. B.C. Moore, ''Effects of Gas Condensate on Cryopumps", Trans. AVS Vac. Symp. i, 212 (1962) 13. R.P. Caren, A.S. Gilerest and C.A. Zierman, "Thermal Absorptances of Cryodeposits for Solar and 290°K Blackbody Sources", Adv. in Cryogenic Eng. i, 457 (1963) 11'. W. Pierce, "Instrumentation for Vacuum Systems", SLAC-TN-64-74 ( 1964) 9 -P, -------- L ------..i---L --1 pump speed= s Qo Qd Qs Q6 ,9 Q7 8 ' Qs Q' s Qp QB QL QM Qw Qw QT ql2 q23 s 23 12 Silver surfaces of resonator (1,2,3,4) - Aluminum surfaces of resonator in duct (10,11) - Stainless steel surfaces of chamber outside resonator (5). Stainless steel surfaces of chamber behind resonator (6,9). - Aluminum surfaces of resonator not through duct (7,8). - Polyurethane chamber seal. Polyurethane valve seals for diffusion pumps. - Permeation through chamber seal. - Gas load associated with loss of beam. Real leakage rate - Mechanisms inside chamber= Q5 • Gas load from all sources, not pumped via duct of length L23 , perimeter H23 , conductance C23 . - Qs + Q6,9 + Q7,8 + Qs + Q~ + QP +QB+ QM. - Total gas load= Q0 + Qd + QW. - Outgassing rate/unit area of the chamber duct walls between p1 and p2. - Outgassing rate/unit area of the resonator duct walls between p2 and p3 . - Pumping speed on one half of the chamber. FIGURE 1. SOURCES OF GAS LOAD FOR HALF THE CHAMBER u w en ' w 0:: _J 0:: 0:: 0 .. 0 010 <t: 0 _J en <t: (!) 161 162 163 164 165 10 100 1000 FIGURE 2. GAS LOAD DURING PUMPDOWN • TOTAL GAS LOAD a. MASS 18 GAS LOAD [!I MASS 28 GAS LOAD 0 MASS 2 GAS LOAD w MASS 44 GAS LOAD PUMPING TIME: MIN. VACUUM CMAMBER -~ 12•; VAULT &--¥• l5 -~ I 1---------------,- -~ - - - - - -To BACK\MG ._, ___ .. ,.,. SYSTEM THRO'TTL'E -I'50LA"TION VALVE, REMOTE CONTROL COl-0 TR~P LEAK TEST CONNECTION ISOLATION VALVE - M,..._~U"-\.. ISOLATION VALV'E. - ~E.t-'\O""T'E. FLE.)(IBLE. S'ELLOW~ SC.REEN AUTOMATIC VENT V..._LVE MOL - SIEVE 'TRAP EiAUGE TUSE Soo C.FM SLOWER ISO C::.FM RO,~'R'( SP,..._RE CONNECTION OIL TR~P LINE TRAP NOTE.: 1- ~YSTEM ~'<MMETRIC.AL. 2. ADDITIONAL DOTTED LINE AND VALVE REClUIRLD FOR D.P. S'(STEM ONLY. 6) ROTM'f'l:~ ---- TO OUT S\DE '-w SCHEMATIC OF ROUGHING TR I U Mr 5YSTE M COMPONENT S-CRVOSYSTE WRIGHT ENGINEERS LIMITED mwH (i)__ ~AAWINII " 0 • \V VANCOUVER-----CANAOA OAT< 2 /<,;, / '-9 FIGURE 3 1 a: 0:: 0 I-w a: ::) V) l/) 10-3 ,02 101 10° ,0-1 102 -3 10 WI -5 a: 10 0... a: w (fl <( I ' I I I I I I I I I I I \ \ \ 3 I \, '--, I 5 --v \ 8 \/ I I. F\OU GH I NG LI NE. TRAP COOLE.D. 2. BLOWERS STARTED. 3.DIFFUSION PUMPS THROTTLED IN, 4. BAKING STARTED. 5. PEAK OF BAKING. "· £NO OF BAKING. 7. F\E SONAT ORS RETURNED TO OPERATING TEMPERATURE. li(CRYOPANELS COOLED. 8. CRYOPANE.LS AT OPERATING TEMPERATURE.. - - -MASS 18 ----MASS 28 -- - SCS TOTAL (P.) I 0 i...:..:: ~REQUIRE.D SCS - I I ---=--=-------- WEIGHTED TOT.AL 108 I I l 10 100 O o W CRYOPUMP SYSTcM TR.l·LJMF PLOT 01= CHA.MSER f'RE.SSURE VERSUS .. PUMPIN~ TIME WRIGHT ENGINEERS LIMITED D~AWN .R _ ____ DRAWING No. \V VANCOUVER-----CANADA DAT[ 2~-= G-_G;,9 PUMPING TIME: MIN FIGURE 4 I ex: CL 0 I-.. t.J O'.'. ::> If) 1/1 t.J IX a. CL t.J cD 101 ,0-1 <( ~--:I u i l I I I I I I I I I I I I \ \ \ '-1 I I 5 . 4 ~------------ + I/. ------f/ 7 !. , I e '- \ + j \f ·=----==---~. ~-~--=- ---0--- ~-I. ROUC,~INC:, LINE C.OLP TR..C..P COOLE..D 2. BLOWE.RS STARH:.t> ~. DIFFUSION PUMPS TI..\ROTTL.E.0 IN -4. l!>Al<.INC:, !:>TA.R.i"E.t) S. PE.Al<. 01= e.AKlNQ ~- E.NP OF e>Al<..ING ,. R.E.!:,ONP.TORS RE.Tl.lR.NE.O TO OPE.RATING TE.M?'c:.RATUR.~ 8. PESIG.N PR.E.SSUR-E.. RE.AC. I..\ E. p --- MA!:,$ 18 MA.$$ 2.8 -- - SCS TOTAL (P.) RE.Ql.lll\Et> ~C.S WE.IG\.\TE.O 'TOTAi.. ,o-s'------'-------'--'--'--'--'-"--'---'--------'--L---'---'---'----'-..l-1.-'-----L--.......___,___.__,--'-_._L..L ___ _.__ _ __.__.1,__......._.L_J,_l_...L..J I 10 100 1000 10,000 PUMPING TIME: MIN W 32." DIFFUSION PUt--1P 5YSTEtv1 TR I U MF PLOT oF CH/'\MBER PRESSURE VERSUS PUMPING TIM£: WRIGHT ENGINEERS LIMITED DRAWN BY w DRAWING Ni. \V VANCOUVER----CANADA DATE 23_ -6- G:, I , FIGURE 5 1T I 0 ...,____ ..... w ..J 4. w 1/) UJ ,> \{I ..J 9w ..J ... uJ < Ul " I t----1 II I ~r+i 1.__ .... 111 ... -4- ...... m-~ 4. :I: IJ. TRIUMF Q. 4: tJI. l-a .J 0 \.) a " -= ttl IO rli w 0 z J >-0 lU ( -OVERALL DIMENSIONS 3e- DtF'FU510N PUMP5 © z 0 -w IJl w WRIGHT ENGINEERS LIMITED Drawn li!...:J'" Appr. OR AWi NG NO. VANCOUVER CANADA Check ~gf!· A REV ...0 uJ a: ::> c.:, I TO BAC.K\NG SYSTEM DIFFU5\0N PUMP COMSIN.-..TION COLO TRAP ,HR.OTTLE-1 ~oL.-..TION V""'-\..VE STACK GAUGE FORELINE VA.LVE FORELINE GAUGE FORE LINE TRA..P 1 0 LNz. r----------- S"<S'TEM '--------f I I ______ _J W SCHEMATIC OF Dlf"FUSION T~llJMF PUMP STACKS 32" DIF"fUSION PUMP SYSTEM £'t; WRIGHT ENGINEERS LIMITED DRAWN _ 0 ••woNo ND. \V VANCDUVER----CANADA DAT< 1c;.- <---~ FIGURE 7 VAULT To D\FFUS\0N PUMP SYSTEM 800 CFM BLOWE~ \50 C.FM ROTAR'( LEAK 1ES1 CONNECTION 1'50LAilON VALVE.- MANUAL ISOL A"T\Ot-1 VP..LVE- REMOTE FLEXIBLE BELLOWS 300 MESH 5CRE"EN • AUTOMA"TIC VENT VALVE MOL - SIEVE TRAP 6A UGE 1U8E LINE TRAP OIL TRAP 5PAR E C.ONNECTION I I EXHAUST TO Al 6 '-' I v~ @ TO ROUGHING. \------_J_--f---i)lc::J---------------1---- 'E>YS, EM NOTE: 1. 5YS1E:M SYMMETRICAL z. ROUGHING SY5TE~ Ac,s A.~ ST,t>..NDBY FOR EITHER BLOWER OR ROTA.RY E')(HAUST TO A.IR '-----~ OISP<>S~L SYSTEM W SCHEMATIC OF BAC~ING TRIUMF SYSTE.M COMPONENTS 32'' DIFFUSION PUMP SYSTEM ~RIGHT ENGINEERS LIMITED DOAWH R DRAWING Na. \V VANCOUVER-----CANAOA DAT< \7- 6- "'~ FIGURE 8 :> 1-z ._ w > L C\I z _J J I..) tu w >-l J lll. 0~ L) II) TRIUMF -,. 19 z ... -a 1/) ID J j :::J 0 II) Cl. ... 0n.. ' Ol z " 4 0 Ill C\Jnl z ll rn I-...., ll X () I&) u J u.. U) II) -- --GI" -2 t-<< w :r z t- \J 0 z }{ uJ w iii~ IQ ~w ~I " - J iJ} (L 0 2 '}/.,-.... LI.I ZrJ l\l ~ILi iii .... _ )( a WW uJ J UJ Q. _J ~"' IL t\J u} ::> z flt 1/) Ill J c,J "' 1/) z l'<IJ Z>-J~ FIGURE 9 -DlrfUSION PUMP SYSTEM REF~I GER.A.TION FO~ C.OL..D T~A.P.S w WRIGHT ENGINEERS LIMITED ... o_r_aw_n_l2._1'J" __ ._A_p_p_r . ...,_ _ _J-----.,--...;;D_R_A,...W_I .;..,N,...;;G~N..;.,O.;:;..;;.... --+-R E_v. VANCOUVER CANADA Check ~gr;· A ~ CHflM8ER Wf?LL ~ / /, ,/ / / / / / / / / / f / / / / / / / / / / ,/. / / / uUPA::JRT £'OD .5" LA _,, ------i le'' ----------==------\ NOTE --HA = HIGH .4B.50RPTANCE LA = LOW RB50RPTRNCE FIGURE 10. CROSS-SECTION - CRYOLINE CONCEPT f?PT#UR O. L./TT.t.E"INC, / 5" ~ CHRMBE.R Wf1Ll ~ // TYP.-!N,-ERMlTTEf/T WELDS ST/F;:E/-./E,E' j'IO x.08' e!VET(TYP) NOTE: HA - HIGH RBSORPTPNCE LA - LOW H'B5a<?PTl'7NCE 5 STIFFENER St/PPcJRT Rt:JD 80° FRONT SHl£LD 3 64 /4 FIGURE 11. CROSS-SECTION - FLAT-SHIELD ARRAY CONCEPT / SUPR:JRT eoo r?R.11-lue o. L/TTLE /,Ve. 5" ,__._ _________________ /3; '-' -------------------------,-, H4 HA =- HIGH r?c350RPTH'NCE LA = LOW r-l/3..50/?PTqNcE CHAMBEe /,MqLL PLATE fJNGLE STIFFENER C/-IEYRO/JS FIGURE 12. CROSS-SECTION - CHEVRON ARRAY CONCEPT flLL EXTERIOR SUR,C-M'CES LA r4LL SURF~CES HA (6?.RTHLIR a Lim~ /AC, L&J (.) z <( I-Q. a:: I 0 o· en m <( 0.8 0.6 0.4 0.2 -3 NOTE= I Torr litre H20 VAPOUR Q! 10 g ,...__ _ B. C. MOORE ( DOUGLAS) CAREN ET AL (LOCKHEED) o ru-..L--.....L-...L.......l.---L-1.~~___JL._..!._L..l......L..l...L.1;J:::---_J_.l...__L.l._...L.l...LLl _ __J_.L.._L_j_..J.....l....L1J 0.01 0.10 1.0 10 100 H20 CONDENSATE DEPOSIT Torr litre/ cm2 FIGURE 13. EFFECT OF H2O DEPOSIT ON ABSORPTANCE 32' I -- RES0Nf1T0!{5 -..-. ~- /7'-+-----~ ..----+----34'--+------+-----. e22I e22I rzzzmzzzzm t22J t'22J FIGURE 14. SCHEMATIC DIAGRAM - CRYOLINE POSITIONS ITl?TWR £1, LITTLE INC,. ,R,RD, 2 7 r-7PPROX, $4' I '-J RESONllTORS 41 ") I-__ 1-... 17' l:J:: 34' 1/ZZi rzzzz$vm 12221 FIGURE 15. SCHEMATIC DIAGRAM - FLAT-SHIELD ARRAY POSITIONS ( eo·K CONDENSE~ -----1 <: H }-- --:> -TL -- {: I :? FEEDTHRO. I CH,&1/v18E£ _ f---W,qLL VGH'5 - -( - 20°k: CONDENSER - ) TL TL --20°.i:: REFRIGERr-1 TOR/ - C/RCL/Lt4TOR - -T -BURST DISC TL - TRf7NSFER LINE FIGURE 16. SCHEMATIC DIAGRAM - 2O°K COOLANT CIRCUIT ----- 561 7.5' -l_ ,/ 29 --!3 f!, ---- • 1ft, L-I V'{_r_ 1;1' CYCLOTRON V~CUUM Cl-lt,C?M 8E E 8· 8tc?YONET Dl5CONNECT REFR!GERRTOI? 4Rr,..,u.-e o.ur:rt.ct#<. C0NN'E"CTION.5 FIGURE 17. PRELIMINARY CONFIGURATION - VJMLI 2O°K HE GAS TRANSFER LINE \ ) -Vf1CUUM JftCl<ET {sTRINL£SS STEEL) INSULf7T/NG SPr!CER MULTI- Ll?YEA' INSULl7TION INNER TU8E (S'i7-?INL€S5 STEEL) TYP/Ct:?L CR05S-SECT/ON -f ...-. -I < ( ( p t I -t::--..5CH£M&TIC LJRt9WING - TYPl,PL. BRYONET COUPLING FIGURE 18. CONSTRUCTION F VJMLI TRANSFER LINE LNz TUE£ LIQUID LJ/\IE SPr?CE,/2 VtctCUUl\/1 JPCK"'ET /NOTE: CONCEPT PROPOSED BY ) ( , Cl?YOGENIC ENGINEEKING ca, .DENV£~ COLOR~DO FIGURE 19. CROSS-SECTION - VJLNS TRANSFER LINE LIQUID LINE I LNz TUBE V&CUUM - . I I ' r r--- FLE,X HOSE /FLEX HOSE UNION COUPLING • ITd~ I I I I Mr-7LE L34YON£T rEMr-7LE c¥1YONEr SHIELD /NOTE: CONCEPT PROPOSED BY ) ( CRYOGENIC ENGINEEE'll\tG CO. DENVE.e', COLO.RROO FIGURE 20. BAYONET COUPLING - VJLNS TRANSFER LINE ..5PRCERS \ I I >--+--II I 1 • \\ \\ ARTHUR ». LITTLE /I.JG. ( RE~R SHIELD ) ' ' ( FRONT '..SHIEZO ) ----i ]7 ]-, }---(I-• ~> - .. -~ J ~: ..... 6 Tl ~: .. -... I ... _ ... -C:-l-l&MBEE?_ <J--( & H 1---1 FEEOTl-/l?Ot/G# W/!?LL ( FRONT SHJELO , ( RSR...5H/£LD Tl 80°K - REFRIGER~ TOR/ C/RCUL./1 TOR ..A. T -BUl?ST DISC ~-R.OW Bi471.t'9NC/NG YtC?LJ/£ TL - Tlf'RNSFEe UN£ ) ) FIGURE 21. SCHEMATIC DIAGRAM - 8O°K COOLANT CIRCUIT TL TL 351 1- \.'-ODA' IVl\l_l?.•-A ~1 -J. I / ' 29 •fr/ ,ro,,,.;!1/... CYCLOT20N V<_:::?Ct./t./M C~MBEe V- Vf7LV£ 8- 8r::IYONET Ol.5CONN£Cr ( )- NOMINRL LIN£ D/RMETE/? 9 - DENOTES LIJ./£ SIZE Chl.4N'GE REFRIGERllTOR .4eTHue o. LITTLE 1Nc. CONlvcCT/ONS FIGURE 22. PRELIMINARY CONFIGURATION - VJR 8O°K CIRCUIT TRANSFER LINE TWISTED-TEFLON-STRIP /NSUlr4TING SPeC7C£R PROTECTIVE PL/-lSTIC COYER HEL/01L-CORRUGtc!TED COPPEE' TUBES ( SE Ml FLEX TM 'A" -VACUUM BARRIER CORP.) FIGURE 23. CONSTRUCTION F VJSF TRANSFER LINE .-<-?RlJli./,2 £).LI T,TL E /NC. 4-/ 31:,' /29' CYCLOTRON //H'CUUM C-Hf1MBER V- YiC/L//E B- f34YONET DISCONNECT M - V&CUUM JVMPER REFR/GEJ?:TTOR ,,:;,ev-1u,e 0, LI vu· l)L'. CONNECT/ONS FIGURE 24. PRELIMINARY CONFIGURATION - VJSF 8O°K CIRCUIT TRANSFER LINE Vf?POUR BARRIER r-RLL METRL FIELD COUPLI/\K:J SOFT .SOLDE'RED "'-...- ""-""--,,-- ""--- ""'-- I I I I "- ......._ ......__. ,~ I I I I I I / ......._ ,,.._ ""-- I I j I I J /"'--'5H'OP Ff18RICRTED SECT/ON F /LJEEGL~SS /,,.W-t.lL& /?~N FIGURE 25. 8O°K TRANSFER LINE BULK INSULATION CONCEPT &RTH~/2 £', t..1rr,e ;;t,l'~ \/ENT COM MERCI A'. LN2-S..JPPL.Y ,__ _____ 'I w _J IL L 11.1 l() 0: '2O05\A. 5000 U5GA.'. LN '2 5TORAGE E >(PER \MEN TA ___ :;p,...,_., I,.___.,.., __ ___. user x "'I~ ~i w l() 8o°K REFRIGERA.l'OR 5TA.1'JO·B LrJ2 C1RCL.JLA.TING '20°K PuMP REFRlGERA..'TOR 1-\,: 5iORAC.e!. 7 7 311 Q 5UPPLY 2O°K ~lTA.1'.lO·BY REFRlGERA."TOR 80°\..;, Rei=R lG'ERAT0R LN2 A.ccuML.lLATuR & RET ._JAN Put-.1\P Ill .J IL UJ l() lt-Je -Gl'J? 300"1< -\/A.ULT -5EM\l=LE')(. (No~-PLA.5"TIC) COPPER TL.lBll'-JG -GHe ?( {f l)J 2 ....J G\-\e olo5P5 \.A.. \J.J.L.N 5 (( ':::l 0 r. <( a: (! 4 '::L 0 0 (V W TRIUMF CONF\GURA."TION I 14EMA.TIC oFREFRIGERATlON 5YSTEM WRIGHT ENGINEERS LIMITED DRAWN ,v ~1..C DRAWING No. '\V DATE~---FIGURE 26 u z w 0 _J ILJ 1-lO 1-0 :J 0. . Q Cl rr er Q_ :::i t- :r: 0. 1-llJ a: U1 u I- 1 .. 0 0 )-2 u cO I I I . - -UJ - 0 z LL ::, a: I-J i <( ll 0 I, ' II 0 0 u (( 1/1 0: L,J L,J z l!I z II: w 1,1 I- > J: :::, l!I 8 - z 0: <( > )~ r-CN LU a:: ::) t9 -LL GNe TOLIQUIFIER 1_ ei'o,A._1, L"-1~ FROM Ll(pl.JIFIER I . - . _I~·'~'~ II ,,- J.-. , ' 10N 50LJRCE & Ace EL ERA.TOA Co~TROL ROOM I El. '287-13 EL ~87• 13. __,__,~~~~~~===I~''~ .............. J ===·: lt:t::t:t:c:==================~ == FIGURE 28 TRIUMF ) l~2 PuMPS REFRIGERATOR ( LIQU\ Fl ER). '---R.F. ~WIPMENT. Rc:x::>M tv\EC~A.N\CA.L 5eRVICES RooM PROPoSED LOCA.'TION oi=- LN2 TANK. "w' WRIGHT ENGINEERS LIMITED _D_raw_n-+-c~1.D_. _A p_pr-+. _ _:----.-_..:;;..D_R A...,.....W----'-1 N.,.....::G;___;_;N-=O-'-. --+R_E - IV VANCOUVER CANADA Check ~gr;· A VENT COMMERCl.~L LN e 5uPPl Y 7-------, y. w _j u. D • 'cO P.5.1 A 5000 U.'5. GAL LN~ OTORA.GE Ex PERI \VIENT A.L U'5E --[><J w lf) GN~ e 300°K. i! e,ooK' REFRl<:;ERt:a..ioR REFRIGERAmR 'A w I CIP.CULA.TIN~ [ PWMP tU \{) t,3 LN2 A.ccuMULA.TOR & R~TI.JR\'J PuMP. ---LNt SOP~.1.-'. '20°K Co1..D Bo'i-CbMPRE6SOR '5F :,( VAuLi ~I-le II)~ )-a. ,( a: ([ lf 1 4. "' ':,L b 2 0 ...J 0 (\J <O ~Etv11FLE'){ (No N PLA ST I c) COPPER TUBING \J.J M.L.I, -GI-le 1SoPS.IA. W TRI UMF Co1'JFIGURA"T\ONS1II AN HE MA.TIC OFREi=P.\G ERATla-J SYSTEM WRIGHT ENGINEERS LIMITED o•AwH c:1.0. DRAWING No. \V DAT[ FIGURE 29 ., COM MERCI AL er --, > LNc .5UPPLY :11------,l 1:: trt '2.0P5.I. A.. YA.POUR15ER I lN CIRCULA.TING PWMP 5TA.tJD-SY LN.CiRCULATltJG PuMP E){PERIMENTAL U5E. -750 CFM l\l.l.COMPRE55~ ' He 5UPPLY n _1000U'5GA.L Accurv11 .• U .• ~OR COLD Box. <( £ ~It~ 0) :J: G Ne cs, aoo"K LN250P5\A = y. Ill _J ll 1 w ({) t ---GHe 150PSLA VAULT -GHe () ~i t-COPPER TWSING 5EM I FL.EX (NON PU--.'5TIC) VJ.M.L I ?i a: a: er ..( )L 0 c.u W TPIUMr CONFIGUR.A.TIONS'v'6tvl 5cHEMA.TIC al=' REFRIGERA.T10N5'1'ST'EM. . WRIGHT ENGINEERS LIMITED o•AwN __ DRAWING No, ~v DATE FIGURE 30 N'2 TO 5~GE TAi-JK TEMP Co,-.rTROL L --TEMP CONTROL v-, I 150?5.\.A. f I _,j!-----1"------,r-, 1-\ e.A..,. 1 COL o Bo.)(.. El(O\ANGEB y NO'TE,;:,'.· I. CONCEPT PROPOSED BY A.1Rco CR'<OGENICS I~. 2. TuRBl"-IE BRAKE LOOP & BEAR ING GA.S o'Y'5TEM5 OMITTED FOR CLARITY LN2 FROM 5TORP-.GE TA1'.lK l IX) IIIIIE -(1=oR CooLOOWN 81. EMERGEI-JCy') HEAT E~CI-\A"'-GER '--------------:.) )lo,., ---------+-----] &::>0 k TuRB11'JES ,---,..---1---, HEAT ExCI-\ANGER ---------'---------,J > ---------;-----~ G 1-\e To & FROM \-\EA.\ Excl-\ANGERS IN l.N2 OTORAGE TA..NK Gooo 'N @ eo°K GHe To&FROM E'0°K ARRAY Ll,OC)'N @ 20°K I - -L---1---------1- • [:)I<] I J 5TANOBY 20°K TuRe1"-lE -----W TR I UM F REFR \GERA,ION 5Y51EM FOR COIV\Bli-..ls:5 80°K-i-20°K l A WRIGHT ENGINEERS LIMITED o•AwN Cl.0. \V DATCi/..... FIGURE 31 D "12 Ll2..JIFIER D 5TAND·BY N'2. liQUIFIER D N2 l !QUI FIER t-..bTE:----· CONCEPT PROPOSED BY AIR PRODUCT5 &C~EMICA.l5 INC To &FROM ~Ne ':STORA.GE TA.l-JK. _.---::;, ------,--1 LN2 l!JI~ .._.---,r---L j.T VA.LVE HEAT Ex.c.1~eR5 Q50ok - ·--~ I -t5rool< r L~e I 1n~, > I E~C~ANGERS I, 7 ,I I/ < / J-T I VALVE. I -t 30f>i< ~~oK Q. I I _J VACUUM 0--IA.M.6e.R H2 Boosi-e~ 5T~D-BY \-\'2 BOOSTER l-1'2.BOOo•ER H2Cotv1~E"SSOA H2CoMPRE550R H'2 CoMPRES50R FOR TPIUMF REF'RIGERATIOl'-J 5Y6TEM r-JERA"T'I~ oF£'ak 'NIT\4\N VA.ULT ~t; WRIGHT ENGINEERS LIMITED DRAWN -~o__ IRAWING NI. \V DATE FIGURE 32 CotviPRE~50R AccuM R l'-JOTE5'.· Gti0 I. Cot--JCEPT PROPOSED BY A.1Rco CR'<OGEN\CS ltv::. --,.;;...._~H><lfT---- _FROM He GAS ACCUMULATOR -t-..iz m _ 5~GE TA.NK CO!vl PRESSOR ---2 ' 1-------~-- -- ~-,- I I 2. TuRBl"-.lE BRA.KE LOOP & BEAR ING GA.S 5Y5TE"'15 OMITTED FOR CLARITY E~C~A.NGER I COLD. Box I .._____ I • y c~~:OL.+! 1 l 1r;:;..a.-'-'-'-...c.......c~'-=-- : LN2 FRoM 5"1DRP..oeT~t-..JK :r I -(FoR CooLOOWN &.EMERGENCY'), ~--------------1-----:J .... GI-le To&FROM 1-\EA.T ExcHAl'--IGERS I I _...,_ __ ...,_ _ ---i-----:J 11-J lJ,.J2 5TORAGE: TA.NK 6000'N@ 60°K, L -- --- - --- - --J. T VALVE 5o°K TuRBINES.7 I I TeMP - I r _L I I 1 ~:J~GER AAA ..,.,, •-....... 1 r-V L He STORAGE (2SOL) Co~~ I I 1 ~i~~ANGER I l • I' ) ii I ~J GHe To&FROM eo°K ARRAY I I I L---1-. - ••,-----------l·'""----:, __, 400 W @ 20°K . 0 _____ ---1-- • C)I(]--== L 5T~ND8Y ict'l( Tu861"-.IE= WI I MODIFICATION OF AIRCO C TR IU MF REFRIGERATOR FOR LIQUEFACTION FOR EXPERIMENTAL USE ~, I';;- I WRIGHT ENGINEERS LIMITE01DRAWH __ • --, ,,. VANCOUVER-----CANADA DAT<~----FIGURE 33 Of" HELIUM DRAWING No. l __ J 2.0°K --- 20.0° K REFi.lG . .,__ _ _;_:;;........D(]____..,._ ____________ _,_ __ ' COLD l=AN TO VE.NT f LIQUID HELIUM FIGURE 34 TRIUMF SCHEMATIC OF LHe STO~I\GE TO Pe..OVIDE 5TA.NDBY ~EFEIGE.eATIOt-J ~T 20° K "vi WRIGHT ENGINEERS LIMITED Drawn etJ' Appr. VANCOUVER CANADA Check ~gr;· DR AW I NG NO. REV TO ROUGI-\INGi SY&'TEM 1011 OIL 01FFU510N PUt-1P5 10• c0Me1N,e,...,10N COLD T",e,...ps 10 11 "THROTTLE -t~OL~'TION \/A\.\/E 5TAC.K &AU GoE (c1;:>LD C.P...1HOOE) F0RELINE GiA U GE (THER.MOCOUPLE) FORELINE y,e,...\..\/E (t11'NU,.._\.) AUTOMATIC. VENT VALV~ PUMP GAUGE MEC.HAHICA\.. PUMP FOREUNE "TR,i.P FLE')(le»l..E BELLOW 5 MOL- SIE\IE "TR#l,.P OIL TR,,._P FORELINE TRAP OISP0~#1o..L. 5'C'5TEM I ~- - -====r - - -~-~-------00 ---:----~-----;-[.O:J-~ -------CRYO-GiEHERK' :4 W CRYOSYSTEM TRIUMF AUXILIARY DIFFU~IOM PUMP SYS :T\C n; WRIGHT ENGINEERS LIMITED D ...... •v __ _ \V VANCDUVER----CANAOA FIGURE 35 COLD TRA.~5 ON AUX\L\ARY D\FFUS\ON PUMPS TRIUMF ... 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VANCOUVER CANADA Check ~gr;· A CA.L\8AA7"ED lEA.K ·/ MAIN 5EAL V= 3100i=T 3 ~ELILJM~ ~,t~5S-----------: -, ----OPeJ ·cLo5EO. -+--IOO%He 5PECTROv1ETER . TRIUMF FIGURE 41 / RouG~ING OY5"iEM. (No"i OPERA1lt--JG). CoNF\GURAT\ON 111=0RSTA1\C H.a.1UM MASS SPECT'R LEAK TEST 'N111-' ?o..lGM1::t 5Y5"iEM w WRIGHT. ENGINEERS LIMITED 1-D_ra_w--tn _c1.._0--+-A_p_p_r . ..,__---111---...;;;.D...;.;.R~A...;.;.W_;_I .:..;..N .=..G ...:N_;_O=-:•:__---+R.;.:;.EV..:...a VANCOUVER CANADA Check ~gr;· A CA.LIBRA.TED LEAK ./ I 10' Olf=FUSIO!IJ PuMP 5TA.CK (O?ERATI l\JG). TRIUMF IOOo/o He. ~EL\ Ut'v1 M.o...55 -5PECTROME'TER . FIGURE 42 ~AIN SEAL 100% He 5ACK\l'JG 5'<6TEM (O~ERA'TI~). OPEN ._____, w WRIGHT ENGINEERS LIMITED t-D_ro_w-+n _c:_\. o_· +· A_p_pr.....,. 1----tt---.---D_R~A_W_I ..,.N ..;..G _N_O.;;;....._--+-R_EV---11 U VANCOUVER CANADA Check ~gf!· A
Report
eng
Unreviewed
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivatives 4.0 International
Researcher
Conceptual Design Study for the Vacuum Pumping Systems for a 500 MeV H‾ cyclotron
Text