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Annual report, 1967 TRIUMF 1967

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T R I . U N I V E R S I T Y  M E S O N  F A C I L I T YTR IUMFANNUAL REPORT 1967U N I V E R S I T Y  OF B R I T I S H  C O L U M B I A  S I MON F R A S E R  U N I V E R S I T YU N I V E R S I T Y  OF V I C T O R I A  V A N C O U V E R ,  B R I T I S H  C O L U M B I A ,  C A N A D AU N I V E R S I T Y  OF A L B E R T A  D E C E M B E R ,  1 9 6 7  ^T R I - U N I V E R S I T Y M E S O N  F A C I L I T YAnnual Report 1967P o s t a l  A d d r e s s :TRIUMF,U n i v e r s i t y  o f  B r i t i s h  Columbia ,Vancouver 8 ,  B . C .Canada. December, 1967.Table of ContentsPageSummary 21. Cyclotron Design Study 21 . 1 Magnet 31 .2 Centre Reg i on 71.3 R . F . System 91.4 Orbit Calculations 111.5 Beam Transport 141.6 Vacuum System 142. Facility Lay-out 163. Assessment of Industrial and Engineering Resources 174. Conferences 185. Staff 186. Report 19- 2 -SummaryActivities over the year have been concentrated primarily on thedesign of the 500 MeV negative ion cyclotron. The major effort has gone- intomagnet design, based on model measurements. R.F. system design, using a resonator model, was started and a centre region study is in progress, based on electrolytic tank measurements. Beam transport design has been studied with an analog computer. Vacuum system design has been studied in detail.These design efforts have been supported by a survey of industrial resources for the various types of equipment. Engineering services,asavailable from private firms, have been evaluated.Design of building and site layout has progressed to the stage where an engineering firm can start working out a conceptual design.Pending completion of funding arrangements for the TRIUMF projectthe design work during 1967 has been supported by an interim grant from theAtomic Energy Control Board, at the rate of $100,000 per annum. As thereport shows, a great deal of progress has been made on solving TRIUMFdesign problems with the interim funds but it has not been possible to carry out all of the work, for 1967, envisaged in the TRIUMF Proposal of November 1966.1 . Cyclotron Design StudyAfter a year of detailed study, a number of the main technical problems, envisaged at the beginning of the year, have been essentially solved. Realisation of the desired performance characteristics has modified the size and cost of some of the components, as discussed below - for example the magnet needs to be somewhat larger than previously proposed. Some of the estimated cost increase is expectedto be off-set by savings on various components, such as aluminum coils instead of copper coils, after further engineering studies. None of the design work has undermined the strong position of the H “ cyclotron as the most attractive and least expensive accelerator for the kind of meson facility desired by the TRIUMF scientists.1.1. MagnetSince the magnet is the most expensive single component of the machine and its long delivery dominates the time scale of the project, model magnet studies were started Immediately. Measurements have been made on a 1/20 scale model magnet, powered by a 150 kW, 3000 A, DC power supply with .001% stability. The first magnet model used (Mk I) was made available by U . C . L . A . s  it had been designed, but never used, for a proposed 700 MeV Pion Facility. The magnetic field measuring gear consists of a temperature stabilized Siemens #FC 33 Hall probe,■driven at constant speed in circles of variable radius. The output is read at one-degree intervals by an integrating digital voltmeter, and printed out automatically and punched onto paper tape for further computer processing, or plotted on an X-Y recorder. The system is automated to a high degree and has operated with practically no trouble, A set of azimuthal field curves is shown in Fig, 1, The Hall probe was calibrated and its stability determined in a special calibration electro-magnet against a nuclear magnetic resonance field probe.By the end of 1967 the basic properties of the unusual magnet had been studied by changing two of the six sectors (Mk„I I See Fig.3)It was found that the azimuthal variation (called "flutter") at full radius was inadequate to obtain sufficient focusing. Various coil-  3 -configurations were tried to improve this without having to increase the diameter of the machine, but these proved impractical. It is now expected to obtain the desired effect by an increase in radius of 3 , 5%.An additional 1 .5% has been allowed to decrease the maximum value of the magnetic field to 5.93 kiloGauss, because of the uncertainty in the available data on electric H dissociation. The result is a maximum orbit radius of 302" and a pole diameter of 650". .A new model (Mk III) is now nearing completion. It will be 111 larger and have the proper sector shape on all sectors. it will also be more flexible and the coils will have more ampere-turns. The various methods examined to improve the "flutter" at full radius are described in a TRIUMF Report.'The manufacturing of the huge magnet cores is a major problem.They could be built up from forgings, castings or rolled plates.Consultation with the major steel companies has confirmed our opinion that rolled plates will provide the most economic solution. At the same time there are more companies capable of producing the plates than of making the castings or forgings, and the machining of 10" rolled plates is within the capabilities of various local companies. Therefore, the present model studies are directed towards the plate construction.Some Mk II model experiments were made to determine the relationship between steel tolerances and magnetic field, and to get some idea of the forces and deflections in the cores. Results indicatethat the magnetic forces in the gap are stronger than the magnetic forcesin the cores that try to keep them together. However, the difference is such that carefully designed bolts in the proper places can resist the resulting forces.RRDIU5 3[RVE) rLUTTERr000*01-  k  -o c o i n o c o o t D —' oc \ jo j r ~ o c r > c n  o ^ c o m c o c n r r L n r r —'CjDOCDcnLn O O O H ^ O J C \ J N t \ J W H ^ O O Or - o c n c D o c o o j z r c D o r ' C D C D O J c n  z r o j L n ( D r r ( D n L n o o t > C T ) r r z r  — U N I N U V E R R S T YO S S z r c j j C o r s j c D c n c nco co ro cn (o cn n (o .o n  ^  =r in inCD CD CD CD CD O D O D O O O O O O O O O O  O O O O O O O O O O L O L n L D L O L OO l D i n L n L D L D L D L n L n L n ....................................i n ...................... o  — < oo co n-• — • C M C o z r i n c o r ' C O c n — • — . ^  ^  •ojco=rLncor-coCT) c\j co rr inC\JD_IQ_Q ! [—000'B 000'8 000’-0131 dFigure 1. Example of a set of azimuthal magnetic field curves. The measurements cover two Mk I! sectors (right) and one Mk I sector (left).- 6 -A theoretical study of the effect of magnetic field toleranceson the beam quality has been made and is the subject of a TRIUMF Report.1.2. Centre RegionThe centre region with its centre post and injection system has an important influence on beam properties and structural design.It can conveniently be divided in three separate subjects: a • Centre Electric FieldA 2/5 scale electrolytic tank model of the centre region, shown in Fig. A, was built and shipped to the University of Maryland, where the electric field between resonators and centre post has been measured with the data collecting equipment, built for MUSIC (Maryland University Sectored Isochronous Cyclotron). This study is to determine the shape of the centre electrodes to obtain proper orbit centering and to learn more about focusing and defocusing effects and phase acceptance. The tank covers a radius of 29" full scale.Computed orbits, using the electrolytic tank data, such as shown in Fig. 7, indicate that it is not difficult to arrange for the particles to miss the centre structure on the first turn and still accommodate the injected orbit within the column. It is more difficult to centre the orbits at the same time. The effect of the long gap crossing time at fifth harmonic acceleration appears to be less than expected. This means a large energy gain per turn and large orbit separation,b. Centre Magnetic FieldThe magnetic field at the centre is to be studied on a 1/8 scale centre region model magnet. The larger scale allows better resolution and measu rement's on the axis of the field, where the-  7 -2- 8 -Figure AElectrolytic tank with centre region mock-up.Scale 2:5Figure 5R.F. model, scale 1 :4 Only one quadrant is shown.Figure 6Analog computer for beam transport studies. The top dials set the length and position and the bottom dials the field strength of up to 18 magnets. The trajectories are plotted on the x-y recorder at left.particles are to be injected, and studying the effect of wedges in the gap to increase magnetic focusing. The model has been designed and is under construction,c . 1nject ionThe design of a spiral electrostatic deflector has been studied- analytical ly and a computer program that develops the three d imerrsTcrrrarf contours of its electrodes has been written (see Fig. 8). The effect such an inflector may have on the beam quality remains to be studied; in any case ,detai1ed design studies cannot proceed until results of a) become available. Alternative inflecting systems are also under study.1.3* R.F. SystemA study of the R.F. resonators has to precede any design work on R.F. power equipment, so a | scale resonator model has been built, according to our specifications, by a local company. The plywood-and- copper model is of flexible construction, allowing changes of resonator height and length. It is shown in Fig. 5.Preliminary experiments with a few watts of R.F. power indicatethat one can readily generate the desired standing quarter wave in bothtop and bottom resonators, by only coupling into the top resonators, proving the basic principle to be sound. The required resonator dimensions have also been measured.A feasibility study for the use of insulators to support theresonators is in progress. Various firms, specializing in themanufacturing of advanced technical products have been consulted for the construction of the resonators. It would appear that one of the better designs can be manufactured locally.-  9 -- 1 1 -1.4. Orb i t Calculat ionsThe orbit dynamics programmes obtained from M.M. Gordon (Indiana University) and M. Reiser (University of Maryland) have beerr modified and adapted to the TRIUMF model magnet data. The programmes have been used for the following work;Evaluation of the radial variation of the average magnetic field to check the isochronous condition.a. A study of the beam orbits at large radii in connection with the"flutter" problem, including effects of hill separation, flutter coils and pole tip shape.b. A study of the focusing in the centre region. This work made itclear that a special centre region magnet model was essential toproduce more realistic data.c. The equilibrium orbit programme has been modified, so that it can track an extracted beam from an internal target through the fringe field into a system of quadrupoles.d. A programme was written for axial beam injection which involvesthe plotting of three dimensional particle trajectories in acombination of magnetic and electric fields and the calculation and plotting of the required electrode shapes.e. A programme for computing median-plane orbits in the centre region,using measured electric and magnetic field data, is being used to determine the optimum energy, position, direction and phase.An internal report, describing in full detail the operation and use of each programme was completed.- 1 1 -Figure 7. Electric field equipotentia 1s and computed centre orbits. The feasibility of using a hollow centre post for structural support is clearly illustrated, but the geometry shown is only preliminary.- 12 -Scale: *—1Front view Side viewFigure 8Projections of inflector electrodes as generated by computer. Electric field: 7.1 kV/cm, magnetic field: 342 k G , injection energy: 200 keV. The electric field is normal to the particle orbit. The parameters are only meant as an example and are not final design figures.-  14 -1.5. Beam Transporta . Analog ComputerA hybrid analog computer has been developed to study the- beam trajectory in the transport system. The displacements are accurate to better than 1%. The analog computer can handle up to seventeen quadrupoles and bending magnets. Magnets with non-uniform fields and with rotated pole faces can be accommodated The analog, which was developed under contract to AECL, was taken to Chalk River and demonstrated in June. A report describing the system has been written-? Work is continuing to extend the computer capability to calculating beam envelopes,b . Computer ProgramA computer program has been written for the UVic IBM 360/AA which tracks beam trajectories or phase space envelopes through a specified transport system. The program is also capable of adjusting magnet gradients and/or positions in the transport system in order to design to some prescribed beam condition such as a focus or parallel beam at a target. Identity systems and achromat;c systems can also be designed. An internal report has been written1.6. Vacuum SystemA study has been made of three methods for evacuating the 3000 ft^ chamber: diffusion pumping, cryosorption pumping and acombination of titanium sublimation, ion and cryogenic pump'ng The magnitude of the magnetic fringing fields in the valleys between magnet sectors and the requirement for long uninterrupted periods of pumping makes the use of a pumping system based on presently available titanium sublimators impracticable.-  15 -Calculations indicate that cryosorption panels could be successfully used on the machine. However, these panels are a new development and have not been proven on large chambers operating in the 10 torr range. Operating time between mandatory regeneration of the panels and difficulties in baking the vacuum chamber during this process, to prevent readsorption of gases on the chamber walls, are important practical problems. insufficient experience has yet been obtained to validate the claim that dusting of the molecular sieve adsorbent does not take place.Liquid nitrogen trapped 35" diameter oil diffusion pumps can operate without serious problems in the magnetic fringing fields and the radiation environment of this machine. In o r d e r  to reduce the presence of oil within the chamber to a minimal value, well designed traps and valves are necessary which significantly reduce the pumping speed of the pumps. Severe space limitat ons restrict the number of diffusion pumps which can be accommodated on the machine.Conductance calculations, based on recent outgassing ate data, have been made of the duct between the upper and lower resonator which links the pumps to the centre region of the machine where the pressure requirement is most critical. The results indicate the extreme importance and necessity for thorough outgassing ol the resonator structure and vacuum chamber. The resonators must be designed such that the surfaces can be baked to 200 C and efficiently cooled in operation. The vacuum chamber walls may be effectvely outgassed by a hydrogen discharge without the thermal expansion and seal problems of a 100°C vacuum bake. Further consideration is given to baking and cleaning procedures prior to welding- A vacuum model- 16 -to confirm the outgassing requirements is being planned.The reliable and widely used method of sealing a chamber roof,48 ft in diameter, is with an elastometer. An elastomeric compound9which can withstand 10 rads will be tested on the vacuum model for permeation and outgassing properties. It is planned to design the vacuum chamber flange to accommodate both an elastomeric seal and a soft metal seal using pneumatic clamps to provide the required sealing forces. The metal seal would not be used until it was anticipated that few openings of the vacuum chamber would be required. All other seals on the vacuum chamber will be metal wherever possible, to reduce the outgassing load and deterioration from radiation damage.A meltable solder seal has received some con s ,deration for the 48 ft diameter seal, and tests on a 2" diameter model were satisfactory using fluxes to obtain wetting of the stainless steel surfaces.However, difficulties in manufacturing a reliable 160 ft seal which is free from real and virtual leaks for long periods of time should not be underestimated. A new aluminum wire sealing technique is proposed for the rectangular metai flanges for beam exit ports, pump, trap and valve flanges.2. Faci1 i ty Lay-outThe Ik B.C. Board of Governors approved a larger site for TRIUMF since the Proposal clearly indicated that the original 4 acre site was too small. The present site is 6.58 acres and also has a better (rectangular) shape. The new site is shown in Fig. 2.An improved site and building lay-out was worked out, taking into account future development of the facility, and 'ssued as internal report.In October a contract for site exploration and conceptual building design and site lay-out was awarded to a local engineering company, made possible by a special grant from U.B.C.3• Assessment of Industrial and Engineering ResourcesTo obtain cost estimates and to ensure a realistic design for the major components, such as magnet cores, magnet coils, R.F. resonators, vacuum equipment, R.F. and D.C. power equipment, etc., contacts were made with various potential manufacturers. It has become clear that the specifications for most of these components will approach the present limits of industrial capacity and capability in size and quality. In some cases the unconventional nature of the job may make it difficult or expensive to obtain competitive bids and some form of cost and fixed profit contract may be necessary.After publication of the TRIUMF Proposal a number of engineering companies offered their services to the project on their own initiatve, while others, likely to be interested, were Invited to submit a proposal. The result was a total of 11 proposals for engineering services, three from U.S. companies, three from Eastern Canadian companies and five from companies in British Columbia.Although this project does not really lend itself to a turn­key contract because of its unprecedented nature, some companies offer something that resembles it, while most companies include project management in the services offered. The type of Project Organisation best suited to TRIUMF and the selection of companies w i ’l be dictated by the requirement of obtaining the best available expertise. A knowledge of local conditions is one facet of the expertise--  17 -Conferences- 18TRIUMFDelegatesU.S. National Particle Accelerator Conference,Washington, D.C., March 1967 2Symposium of Pacific Northwest Section of the American Vacuum Society,Portland, Oregon, May 1967 1International Conference on High Energy Accelerators,Cambridge, Mass., September 1967 1National Symposium of the American Vacuum Society,Kansas City, October 1967 1International Magnet Conference, Oxford, June 1967 15. StaffTRIUMF Employees;Research Engineer J.J. Burgerjon (from 1 July 1966)Phys i c i s t E.G. Auld (from 1 September 1966)Computer Analyst D.B. Scott (from 1 October 1966-30 Sept.6 7 )Research Associate Vivienne J. Harwood (from 1 February 19 6 7 )Draftsman H.G. Bridge (25 July-30 Sept 66) F.B. Banks (from 15 Nov 66)Techn i c ian M. Haines (from 1 September 19 6 6 )Machi n i st M . He inr ich (f rom 1 March I967)Post Doctorate Fellow R. Cobb (UVic) (f rom 1 September 1967)Summer Students Miss 1. Hor, Miss J . ArgyleGraduate Students S. Oraas (from May 1967)R .J . Lou i s (f rom September 1967)N. Al-Qazzaz (UVic) (f rom September 19 6 7 )Faculty (part-time)J,B. Warren, E.W. Vogt, M»K. Craddock, K.L. Erdman, G. Jones, D.L. Livesey, B.L. White, R.M. Pearce (UVic), L.P. Robertson (UVic), D„ Lobb (UVic),B.D. Pate (S.F.U.)Consu1tantsJ.R. Richardson (University of California, Los Angeles)M. Reiser (University of Maryland)KoR. MacKenzie (University of California, Los Angeles)-  19 -The TRIUMF Steering CommitteeJ.B. Warren (Chairman)E.W. Vogt J„J, BurgerjonB.D. Pate (Simon Fraser University) R.M. Pearce (University of Victoria) J.T. Sample (University of Alberta)A complete list of members of the TRIUMF Study Group (E.W. Vo g t r Chairman) can be found on p.5 of the TRIUMF Proposal.Initial model magnet study for a 6 sector 500 MeV H" cyclotron.Magnetic Field tolerances for a 500 MeV H” cyclotron.A hybrid analog computer for beam optics calculations.6. Reports1. TRI-67-12. TRl-67“23. FSD/ING 97


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