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Study of self-supporting deuterated polyethylene targets Makosky, Lyle M. 1969

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A STUDY OF SELF-SUPPORTING DEUTERATED POLYETHYLENE TARGETS  LYLE •Sc.  M.  (Hons.) U n i v e r s i t y  MAKOSKY o f Western O n t a r i o , 1  A T H E S I S SUBMITTED IN P A R T I A L FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE In t h e D e p a r t m e n t o f PHYSICS  We a c c e p t t h i s  thesis  as c o n f o r m i n g  tothe  requi red standard  THE UNIVERSITY rfF B R I T I S H COLUMBIA June,  1969  In p r e s e n t i n g an  this  thesis  advanced degree at  the  Library  I further for  shall  the  in p a r t i a l  f u l f i l m e n t of  University  of  make i t f r e e l y  agree that  permission  s c h o l a r l y p u r p o s e s may  by  his  of  this  written  representatives. thes,is f o r  available for for extensive  g r a n t e d by  financial  yf3  the  It i s understood gain  permission.  Department of  ^ YS/C  The U n i v e r s i t y o f B r i t i s h V a n c o u v e r 8, Canada  Date  be  British  £ Columbia  ^f^ft?  shall  requirements  Columbia,  Head o f my  be  I agree  r e f e r e n c e and c o p y i n g of  that  not  the  that  Study.  this  thesis  Department  copying or  for  or  publication  allowed without  my  -  Ii -  ABSTRACT  Thin self-supporting reaction  2  H ( H e , p ) H e h a v e been 3  techniques Stable  deuterated polyethylene investigated.  4  f o r the  construction  of  the  10  carbon  layers  690  yA/cm , were c o n s t r u c t e d  T a r g e t s p r e p a r e d by stronger  than the  The  targets  the  first  the  pouring  2  yc o f  3  initial  He  p r e p a r e d by  the  target.  the  C^D^molecules  into their  diffusion  the  d e u t e r i u m out  of  targets  The  d e t e r i o r a t e by  MeV  the  protons  associated  from the  reaction  t e c h n i q u e , were measured. protons  i n the  backed heavy  present  The  deuterium content of  the  thickness  alpha y i e l d per  10  the  from the  yg/cm  2  carbon  was  used  the  carbon  reaction l a y e r on  2  proton  this  and  initial  reaction The  during  subsequent effect,  the  relevant  the  3  "back" of  the  observed with  section  f o u n d t o be  comprising  section  a  target by  the  copper  by  68).  of  "sandwich".  t a r g e t , and  the  (Ho  function  a f a c t o r of  the  this  by  measurements  linear  of  to  scattering suffered  than that cross  cross  beam p r o f i l e s  3  H ( He,p)^He i n c r e a s e d the  (C^DiJn.  of  yc.  smaller  layers  mechanically  is a t t r i b u t e d . to  H ( He,p)^He, which are  t a r g e t was  thick  2  deuterium content  After  technique.  in previous  densities  yg/cm  t o be  effect  amount o f e l a s t i c  targets  ice targets  of  The  2  tested.  atomic constituents  for total  particle  10  evaporation  This  per  evaporating  ("sandwich" t a r g e t s ) .  i n the  target.  l e s s t h a n 0.05%  t a r g e t s were d e v e l o p e d f o r use  m e a s u r e m e n t s by 15.8  the  the  beam c u r r e n t  t e c h n i q u e were found  breakdown of of  He  film  +  rapid decrease  beam on  3  f i l m were  evaporating  (C Di )n  the  "sandwich" targets  e x h i b i t an  150  of  with  B o t h p o u r i n g and  keV  by  2  onto both sides  f o r use  polyethylene  t a r g e t s , capable of w i t h s t a n d i n g  o f more t h a n  targets  The 1.83  a factor  of  0.35  -  1.38  - 0.26  p e r 10 y g / c m  a possible explanation repleased and  2  carbon  of t h i s  from the polyethylene  i s t r a p p e d by t h e c a r b o n  per carbon  atom.  iii  -  l a y e r on t h e " f r o n t " o f t h e t a r g e t .  effect  i t i s proposed  that  deuterium,  by t h e beam, d i f f u s e s t h r o u g h o u t  to a concentration  o f 0.11  As  deuterium  the target atoms  iv -  TABLE OF CONTENTS  ABSTRACT  i i  TABLE OF CONTENTS  iv  L I S T OF TABLES  v]  L I S T OF FIGURES  v i i  ACKNOWLEDGEMENTS  x  CHAPTER  CHAPTER  I  II  INTRODUCTION 1.1  General  Introduction  1.2  P r e v i o u s Work w i t h P o l y e t h y l e n e T a r g e t s  1.3  P r e s e n t Work w i t h P o l y e t h y l e n e T a r g e t s  EXPERIMENTAL METHOD AND 2.1  General  2.2  Target Preparation  2.3  2.4  1 8 10  DESIGN  Introduction  ...  13  2.2.1  C a l i b r a t i o n of Thickness Monitor  1**  2.2.2  Poured  18  2.2.3  Evaporated  2.2.4  Target  Alpha  Yield  Polyethylene Targets Polyethylene Targets  23  S t r e n g t h e n i n g T h r o u g h R a d i a t i o n ..  25  Measurements  2.3.1  Method  2  2.3.2  Apparatus  30  T a r g e t T h i c k n e s s Measurements  By E n e r g y L o s s  7  AE  2.4.1  Method  36  2.4.2  Apparatus  39  -  CHAPTER  II  EXPERIMENTAL METHOD AND 2.5  CHAPTER  III  DESIGN  continued  Measurements  2.5.1  "Coincidence" Electronics  42  2.5.2  Other Apparatus  45  EXPERIMENTAL OBSERVATIONS  and Method  AND  CALCULATIONS  3-1  General  3.2  Self-Supported Target  3.3  Target Performance  Under t h e He  3.3.1  and E n e r g y  3.4  52  Introduction  52  Preparation 3  Alpha Y i e l d  3.3.2  IV  -  P r o t o n Beam P r o f i l e  for  CHAPTER  v  Beam  Loss  Thickness  Alpha Y i e l d  P r o t o n Beam  65  ..  76  Profile  O p t i m i z a t i o n o f Measurement Parameters  3.4.2  Horizontal  3.4.3  Vertical AND  .  f o r Carbon Layer V a r i a t i o n s  3.4.1  CONCLUSIONS  56  R e g u l a r Runs  82  Profile  85  Profile  SUGGESTIONS  4.1  General  88  4.2  S u g g e s t i o n s f o r F u r t h e r Study  Conclusions  94  96  BIBLIOGRAPHY APPENDIX A  (C D )n  APPENDIX B  ENERGY LOSS OF THE H e  APPENDIX C  THE "EQUIVALENT POLYETHYLENE T H I C K N E S S " AS A FUNCTION  2  [ +  3  OF THE ALPHA YIELD APPENDIX D  97  THICKNESS REQUIREMENT BEAM  IN A CARBON F I L M  (COUNTS/yc)  99  1Q  1  "EQUIVALENT CARBON T H I C K N E S S " OF TARGET MATERIAL CALCULATED FROM THE  1 9  F RESONANCE SHIFT  IO * 1  - vi  L I S T OF TABLES  TABLE 1.  Layer thicknesses  and t h e i r e r r o r s f o r t h e " s a n d w i c h "  targets 2.  A summary o f t h e a l p h a testing  3.  5**  carried  carbon  Attenuation different  and e n e r g y  loss  thickness  o u t on t h e b a s i c " s a n d w i c h " t a r g e t s a m p l e s . .  A summary o f t h e a l p h a different  yield  yield  study  on t a r g e t s  with  layer thicknesses  of the proton  h a l f angles  beam  58  66  (due t o s c a t t e r i n g ) f o r  s u b t e n d e d by t h e p r o t o n  detector  92  -v i i  L I S T OF  FIGURES  FIGURE 1.  2  H ( He,p) *He r e a c t i o n  kinematics  2  2.  2  H( He,p) He  reaction  kinematics  3  3.  2  H ( He,p) He r e a c t i o n  kinematics  k  3  3  t  l t  3  1+  17  k.  Geometry o f c a r b o n e v a p o r a t i o n a p p a r a t u s  5.  Selective  e v a p o r a t i o n , p o u r i n g and w e i g h i n g p r o c e d u r e s f o r  *»5 y g / c m  thick  2  poured  20  (C Dt )n t a r g e t s 2  f  6.  Schematic diagram of the " s i n g l e  7.  Schematic diagram o f polymer  grain  b o x s o u r c e " ........  strengthening  t h r o u g h gamma 26  radiation 8.  S c h e m a t i c d r a w i n g o f t h e chamber s e t - u p f o r a l p h a y i e l d measurements  9.  31  Block diagram of the e l e c t r o n i c s  f o r the alpha  yield  measurements 10.  11.  33  S c h e m a t i c d i a g r a m o f t h e chamber s e t - u p used  in target ^0  t h i c k n e s s m e a s u r e m e n t s by e n e r g y  loss  Block diagram of the e l e c t r o n i c s  used f o r t a r g e t  m e a s u r e m e n t s by e n e r g y 12.  thickness M  loss  Block diagram o f the e l e c t r o n i c s  used  i n t h e p r o t o n beam ^3  p r o f i l e measurements 13.  S c h e m a t i c d i a g r a m o f t h e chamber  s e t - u p used  i n the proton  beam p r o f i l e m e a s u r e m e n t s 1^4.  2A  Diagram of c o l l i m a t o r and v e r t i c a l  d e v i c e f o r measuring  p r o t o n beam p r o f i l e s  ^6 the horizontal 50  - v i i i  FIGURE 15-  A typical yield  16.  Alpha y i e l d  current  f o r the targets  integrated  61  beam  integrated  64  beam  I I A S ( l ) a n d I IAS (2)  as a f u n c t i o n o f t h e t o t a l  on t a r g e t  integrated  IIBS(l),  68  beam  I IBS(2) and  '  Alpha y i e l d current  f o r the targets  beam  I I IAS (1) and IVo  as a f u n c t i o n o f the t o t a l  I IBS (3) 20.  f o r the targets  integrated  IBS(2) and IBS(3)  as a f u n c t i o n o f t h e t o t a l  on t a r g e t  Alpha y i e l d  57  f o r the targets  on t a r g e t  Alpha y i e l d current  19.  spectrum f o r the alpha  as a f u n c t i o n o f t h e t o t a l  on t a r g e t  Alpha y i e l d current  18.  state detector  measurements  current 17.  solid  69  as a f u n c t i o n o f t h e t o t a l  on t a r g e t  f o r the targets  integrated  IICS(l),  beam  I ICS ( 2 ) R a n d  70  I ICS (3) 21.  Alpha y i e l d current  22.  Final carbon  23.  on t a r g e t  alpha  the  yield  f o r the targets  beam  I I I B S ( l ) and I I I B S ( 2 ) R . . .  as a f u n c t i o n o f t h e number o f l O p g / c m  of the " f i n a l  alpha  yield"  same t a r g e t  in i t soriginal  The r a t i o o f a n t i  coincidence  function of the s o l i d  71  2  73  f o r a given  l a y e r s on t h e " b a c k " t o t h e " f i n a l  alpha  number o f yield" for  " b a s i c " sandwich f o r m , as  a f u n c t i o n o f t h e number o f c a r b o n 24.  integrated  l a y e r s on t h e " b a c k " o f t h e t a r g e t  The r a t i o carbon  as a f u n c t i o n o f t h e t o t a l  layers  to coincidence  state detector  74 counts as a  assembly angle  77  - ix-  FIGURE  25-  The r a t i o o f a n t i function  26.  27.  coincidence  o f the time delay  The r a t i o o f a n t i function  to coincidence  c o u n t s as a 78  of the s o l i d state detector height  The r a t i o o f a n t i function  coincidence  28.  Horizontal  29-  Vertical  profiles  profiles  f o r the proton  coincidence  o f t h e base  to coincidence  of proton  o f proton  pulses  to coincidence  line setting beam  beam  counts as a 79  c o u n t s as a  f o r t h e 100 keV w i n d o w .,  80 83 86  -  X  ACKNOWLEDGEMENTS  I wish  t o e x p r e s s my s i n c e r e g r a t i t u d e  patience of  this  t o D r . C.F. H o j v a t f o r h i s  and u n d e r s t a n d i n g o f t h e problems research  experimental  and f o r h i s s u p e r v i s i o n  involved  during  and a s s i s t a n c e  the course  throughout the  work.  I am a l s o g r a t e f u l t o D r . G.M. G r i f f i t h s  for his supervision  o f my  c o u r s e o f s t u d y a n d f o r h i s h e l p f u l s u g g e s t i o n s on t h e w r i t i n g o f t h i s thes i s.  The  assistance  group  of the students,  i s thankfully  I am i n d e b t e d scholarship  a n d f a c u l t y o f t h e V a n de  Graaff  acknowledged.  to the National  during  technicians  this  work.  Research Council  f o rthe receipt of their  - 1-  CHAPTER I  INTRODUCTION  1 .1  General I n t r o d u c t i o n  The r e a c t i o n for  H ( H e , p ) ^ H e , Q = 1 8 . 3 5 2 MeV,  particle  permits  technique  proton  reaction  (Ho 6 8 ) .  of  c o n s e r v a t i o n o f energy  of the r e a c t i o n .  and f i n a l  o f the incoming  The p a r a m e t e r s  primary  i n the input channel  matical  relationships  Figures  1, 2 a n d 3.  kinematical information.  i s defined by.  particles  reaction,  2  correlating  The r e l e v a n t k i n e -  H ( He,p) He are presented i n 3  4  D e t e c t i o n o f one o f t h e p r o d u c t s  not o n l y d e f i n e s t h e  a s p e c t s o f t h e a s s o c i a t e d one b u t a l s o y i e l d s For example,  Kinematical  u s i n g , f o r example, the  as a p a r a m e t e r .  f o r the reaction  beam,  a r e t h e masses o f t h e  fora particular  t h e a n g l e s and e n e r g i e s o f t h e outcoming  o f t h e two  i s detected at  p r o d u c t s and t h e Q-value f o r t h e r e a c t i o n .  c a n t h e n be w r i t t e n ,  energy  the principles  the c o r r e l a t i o n  and a n g l e o f e m i s s i o n o f t h e a s s o c i a t e d p a r t i c l e  the parameters  incident  state,  I f one o f t h e p a r t i c l e s  some a n g l e w i t h r e s p e c t t o t h e d i r e c t i o n  relationships  from  particles.  i n the f i n a l  and momentum p e r m i t  i n a n u n a m b i g u o u s way.  the energy  techni-  removed by a n a b s o r b e r  by t h e d e t e c t i o n o f t h e a s s o c i a t e d ^He  a n u c l e a r r e a c t i o n w i t h two p a r t i c l e s  initial  c r o s s s e c t i o n s by t h e  ( i e p r o t o n beam a t t e n u a t i o n ) w h e r e t h e p r o t o n beam i s  In  products  as a source o f protons  The a s s o c i a t e d p a r t i c l e  t h e measurement o f t h e p r o t o n s  a p r o t o n beam defined  i s used  3  t h e measurement o f t o t a l  associated que  2  useful  temporal .  i t p r o v i d e s a means o f k n o w i n g when t h e a s s o c i a t e d  ALPHA  ENERGY  (Mev)  PROTON Figure 3  :  ANGLE  2 (3He,p) He reaction kinematics 4  H  - 5 -  p a r t i c l e was p r o d u c e d developed  o r i s expected  by H o j v a t a n d J o n e s  to arrive.  (Ho 68),  In t h e t e c h n i q u e  t h e He p a r t i c l e s o f energy 4  3.3 MeV e m e r g i n g f r o m t h e t a r g e t a t an a n g l e o f 96.2° w i t h r e s p e c t t o the  i n c i d e n t H e beam w e r e d e t e c t e d  The  kinematica11y corresponding  of  3  15.8  time o f a r r i v a l associated  MeV p r o t o n s e m e r g i n g a t an a n g l e  t o be m e a s u r e d .  Both  ^He p a r t i c l e .  identified  particle  Thus, removal  section of different  o f a proton from  2  m e a s u r e d by Kunz  As 3  discussed  3  standing  This associated  reaction  cross  reaction.  The c r o s s s e c t i o n a s  c r o s s s e c t i o n o f 695  -  millibarns  o f ShO k e V .  w o r k , as maximum e n e r g y  l o s s o f 100  t a r g e t i s c o m p a t i b l e w i t h good c o l l i m a t i o n The l i m i t a t i o n  on t h e p r o t o n f l u x e s  keV by t h e i n the  then a r i s e s  not i n  i n t h e p r i m a r y beam f r o m a p a r t i c l e a c c e l e r a t o r , b u t i n  involved i n the design of source  the necessary  scattering  tf  in the o r i g i n a l  the f l u x e s a v a i l a b l e  proton  counters,  i n t h e a s s o c i a t e d p r o t o n beam d e p e n d s o n t h e  has a r e s o n a n t  He energy  (Ho 68).  the problems  3  (Ku 55)  H e beam i n t h e s o u r c e  p r o t o n beam  by a c o i n c i d e n c e .  t o measure t h e t o t a l  f o r t h e H ( He,p) He source  a t an i n c i d e n t  t h e p r o t o n "beam"  absorbers.  flux available  cross section  c o l l i m a t i o n and t h e  by a n a n t i c o i n c i d e n c e b e t w e e n t h e ^He a n d p r o t o n  t e c h n i q u e was u s e d  particle  the spatial  traversing  o f t h e p r o t o n w e r e d e f i n e d by t h e d e t e c t i o n o f t h e  w h e r e a s p r o t o n t r a n s m i s s i o n was i d e n t i f i e d  The  surface barrier detector.  63.5° w e r e d e t e c t e d i n a C s l s c i n t i l l a t i o n c o u n t e r a f t e r  the sample a b s o r b e r  was  in a silicon  targets capable o f w i t h -  beam c u r r e n t d e n s i t i e s w i t h o u t  m a t e r i a l i n t h e p r o t o n and H e 4  paths.  introducing  unwanted  - 6 -  In  the o r i g i n a l  copper  work a heavy  backing f o i l  vapour  (injected  copper  b a c k i n g however  be  2  was e m p l o y e d .  contact with a liquid  Protons  iceD0  The c o p p e r  i n t o t h e t a r g e t chamber)  sample being measured.  scattering  by s u b t e n d i n g  a larger solid  r a t i o o f the detected c o i n c i d e n t protons  by t h e p r o t o n d e t e c t o r .  due  to the e l a s t i c  scattering,  t e c t o r was c a l c u l a t e d number o f p r o t o n s  backed  detected which  t h e c h o s e n ^He p a r t i c l e s  For such  background.  i n an a n g u l a r range  of only  time o f a preceding  t o produce a p u l s e a t a l l , o r i t s p u l s e amplitude  large  with 5°).  in the detectors, a p a r t i c l e  o f a c o i n c i d e n t p u l s e from  5  by t h e p r o t o n d e -  are not a s s o c i a t e d kinematica1ly  the paralysis  disappearance  solid  a large angle there i s a  at  The  by  f o r an a t t e n u a t i o n o f <5 x 10  present  fails  scattering,  i s determined  The p r o t o n d e t e c t o r  Due t o t h e " d e a d t i m e " e f f e c t s  either  backing  to the attenuation  targets,  (which o c c u r  one o f t h e d e t e c t o r s w i t h i n  that attenua-  ( i e detected coincident with  the h a l f - a n g l e subtended  t o be 11°.  contri-  o f t h e p r o t o n beam i n t h e s o u r c e  t a r g e t does n o t c o n t r i b u t e s i g n i f i c a n t l y For t h e case o f the copper  beam.  angle with the proton detector.  t o t h e n o n - c o i n c i d e n t ones  i s chosen so t h a t t h e s c a t t e r i n g  The  the absorber  due t o t h e c o p p e r  The  angle  This w i l l  i s due t o s o u r c e s o t h e r t h a n  be r e d u c e d  ^He p a r t i c l e s )  ice.  of the proton  anticoincidences.  T h i s background,  water  by t h e p r o t o n d e t e c t o r w i l l  can  the angle subtended  t o f r e e z e heavy  a t t e n u a t i o n " o f t h e p r o t o n beam i e  t i o n o f t h e p r o t o n beam w h i c h  thick  kept i n  2  s c a t t e r e d o u t o f t h e a n g l e subtended  the monitored  inch  6  into a layer of D 0  introduced e l a s t i c  t o the "background  x 10~  backing f o i l ,  n i t r o g e n r e s e r v o i r was u s e d  d e t e c t e d as " f a l s e " o r background  bute  t a r g e t o n a 120  arriving  pulse  i s degraded.  the proton d e t e c t o r w i l l  result  -  in  the  r e c o r d i n g o f an  7 -  " a c c i d e n t a l " a n t i c o i n c i d e n c e count.  dead t i m e e f f e c t s were enhanced  i n t h e p r o t o n d e t e c t o r due  background of n o n - c o i n c i d e n t p r o t o n s , a n a l y s i s of both within  4  He  analysis of a  selected  energy.  each p r o t o n 70  x 10  obtain  employed.  1  o n l y 35%  a typical  errors a  time  on  The  this  of a deuterium  polyethylene  type prepared  the e l a s t i c subtended  by  and  occurred  " g a t e " may  pre-  yS g e n e r a t e d  proton  with  r a t e of (Ho 68).  were a n a l y z e d are  To  required.  analyzed,  ( C D ) n f i l m was 2  t t  with practically  scattering  profiles  Hence,  increases  to e l a s t i c (Ho  of the proton  scattering  of the proton  by a l a r g e f a c t o r .  suggested  no b a c k i n g  68).  (Ho  foil  then  be  reduced  by  t h e same f a c t o r .  in  non-coincident  Consequently  t h e " P a r a l y z a b l e Dead T i m e G a t e " w i l l  A target of  at a l l would  beam c o n s i d e r a b l y .  The  effects  self-supporting  The  the proton d e t e c t o r at the c e n t r e of the source  reduced  beam  68).  t a r g e t i n the form o f a  be  by  vertical  target  then  pulses  the  r e q u i r e d f o r measurements.  backing o f the source  deuterated  pulses  16  time" of  He  large  detected w i t h the c o r r e c t  t h e number o f c o u n t s  t h e s p r e a d i n g o f t h e beam due  possibility  4  to the  to prevent  this  l a r g e number o f c o u n t s  A measurement o f t h e h o r i z o n t a l  the copper  ^He  these  purpose a " P a r a l y z a b l e  of  non-coincident  of the d e t e c t e d  t h e "dead t i m e " r e s t r i c t i o n  confirmed  of the  For example, f o r a "dead  low s t a t i s t i c a l  the a n a l y s i s  For t h i s  However, t h e use  large fraction  d e t e c t e d and  S" ,  3  necessary  p r o t o n p u l s e s when t h e p r o t o n  a p r e s e t t i m e o f a p r e v i o u s one.  Dead T i m e G a t e " was vent  and  i t was  Since  the  proton  solid  reduce angle  target could r a t e would  t r a n s m i s s i o n of  increase accordingly.  ^He The  - 8 -  increased errors  result total  calculations  show t h a t a s e l f - s u p p o r t i n g d e u t e r a t e d  have a p p r o x i m a t e l y ice target.  2.5 t i m e s  keV l o s s was c a l c u l a t e d t o be 45.5 y g / c m  I t was s u g g e s t e d non-coincident  The t h i c k n e s s o f ( C D ) n 2  (Ho 68) t h a t  protons  plus  at  the source  in  the coincident counting  target could  uncertainty  thin  Previous  provide  copper backing  horizontal  15 c m  the c o n f i n e s  2  targets  t o produce  this  (Appendix A ) .  through  a factor of k  t h e dead  s e c t i o n v a l u e would  time  gate.  t h e n be r e d u c e d  Targets polyethylene  by O l i v o a n d B a i l e y  600 yg o f ( C D i ) n 2  boiled f o r at least  copper backing.  t  while  (01 6 7 ) .  The t a r g e t s  in 1 g of b o i l i n g Xylene.  The  t e n s i o n kept the s o l u t i o n w,ithin  the Xylene evaporated.  to study  as z i r c o n i u m  t a r g e t s on a  2 minutes and then poured o n t o a  Surface  t o be r e l a t i v e l y (such  2  thick deuterated  t o 160 keV p r o t o n s  t a r g e t s were found deuteride  2  of the target backing  were s u b j e c t e d  target  time.  was d e s c r i b e d  s o l u t i o n was g e n t l y  required  t t  an i n c r e a s e by a t l e a s t  Polyethylene  by d i s s o l v i n g  polyethylene  i n the r a t i o of coincident to  rate transmitted  p r e p a r a t i o n o f 40 y g / c m  were prepared  the increase  i n t h e measured c r o s s  Work w i t h  beam,  t h e l a r g e r number o f d e u t e r i u m a t o m s a v a i l a b l e  5 0 % i n t h e same m e a s u r i n g  The  cross  more d e u t e r i u m a t o m s a v a i l a b l e t h a n  100  1.2  reaction  3  heavy  by  proton  statistical  o f 100 keV t o an i n c i d e n t 690 keV H e  the  The  i n lower  measurements.  an e n e r g y t h i c k n e s s  would  would  f o r t h e same a n a l y s i s t i m e d u r i n g  section  For  number o f e v e n t s a n a l y z e d  The t a r g e t s  the reaction D(p,y) He. 3  s t a b l e and gave a h i g h e r deuteride).  A rapid  y  The  ray y i e l d  initial  than  - 9 -  deterioration (0.3  of the polyethylene  targets a t high  mA/cm ) was o b s e r v e d . 2  G.T. A r n i s o n  (Ar 66) d e s c r i b e d  (C Di )n  supporting  2  targets  t  a technique  2  poured onto a s h a l l o w 100 y g / c m  stripping  2  thick  agent.  for the preparation of self-  in the thickness  w e i g h e d q u a n t i t y o f ( C D t ) n was d i s s o l v e d  a  beam c u r r e n t d e n s i t i e s  steel  I t o 20 mg/cm .  tray  (heated  up t o  T h e s o l u t i o n was  200°C) o n t o w h i c h  sodium c h l o r i d e l a y e r had been e v a p o r a t e d T h e t r a y was a l l o w e d  d i s h o f warm w a t e r a n d t h e f i l m  t o cool  A  2  i n warm X y l e n e .  t  stainless  range  and then  t o a c t as a  immersed  i na  slowly stripped o f f .  The  p r e p a r a t i o n o f s e l f - s u p p o r t i n g (C D )n t a r g e t s o f a t h i c k n e s s equal t o  100  yg/cm  2  0.01  2  was d e s c r i b e d  by T r i p a r d a n d W h i t e  i n 5 9 of boiling  g o f (C2D[+)n  t t  Xylene.  t h e h o t s o l u t i o n was p o u r e d o n t o p r o c e s s were s e t a s i d e tests  indicated that  the  that the evaporation  polyethylene  improved  f i l m with  i t s thin  the  slowly  slide  f i l m s were p i c k e d To  low thermal  the s t a b i l i t y  a great  t h e w a t e r a t an a n g l e  up on f l a t  metal  were C  1 2  (d,p)C  deal.  2  I t was  t h i c k ) onto  The p o l y e t h y l e n e  o f 30° t o t h e s u r f a c e .  frames w i t h  and D(d,p)T and t h e s e  (10 y g / c m  particle  o f f t h e g l a s s by l o w e r i n g  2 MeV d e u t e r o n s w e r e m o n i t o r e d . 1 3  preliminary  conductivity.  0.318 cm d i a m e t e r  measure t h e t a r g e t d e t e r i o r a t i o n , r e a c t i o n p r o t o n s  targets with  The s l i d e s  i n a charged  f i l m o f carbon  c a r b o n c o a t i n g was f l o a t e d  into  Their  unstable  and e l e c t r i c a l  of a thin  f o r 5 minutes  clean micro s l i d e s .  t h e t a r g e t s were very  very  They d i s s o l v e d  After boiling  t o dry i n a d u s t - f r e e environment.  beam d u e t o t h e i r found  (Tr 67).  produced  The  holes.  from bombarding t h e  The c o m p e t i n g two peaks  reactions  i n the proton  - TO -  energy spectrum. the  two  peaks,  polyethylene deuteron  proton  White  65)  (Wh  i n t h e d on  was  what a p p e a r e d  This  described  t o be  production,  reviews  total ice  1.1  (D 0) 2  possible  t o 290°C.  Initial  between the  A°  small  t h i c k on  and  improvements s u g g e s t e d deuterated  t h e p r e p a r a t i o n and  substrates.  t o be  imbedded  into  a  s p o i l e d by  i n them.  The direct  defect.  and  solid  backed  target  s t r i p p i n g o f f procedures  literature  (Ko 66,  Ma  67,  Ya  Targets  the  source  f o r these  polyethylene  testing  glass  s u b s t r a t e prevented  technique  sections of d i f f e r e n t as  1 2  poly-  pieces of Polyethylene  the a s s o c i a t e d p a r t i c l e  w i t h a copper backing  C  loss of  o f common s o l i d  d e s c r i b i n g s e l f - s u p p o r t i n g and  a l s o a v a i l a b l e in the  was  to the  implied a greater  material  source  incident  respect  f i l m s appeared  pieces of s o l i d  reaction cross  self-supporting gate  2500  dropping  Work w i t h P o l y e t h y l e n e  described  proton  and  t h i c k n e s s measurement t e c h n i q u e s  Present  Section  900  deuterated  atoms.  subsequent f i l m s were f r e e from  (from s u b s t r a t e s ) are  1.3  by  small  carbon  in  c o l l i m a t o r there  with  t h e vacuum e v a p o r a t i o n  between  i n t r o d u c t i o n of a b a f f l e  Good g e n e r a l  t a r g e t than  W i t h an  diameter  1 h o u r o f bombardment.  conducted  d e p o s i t i o n and  cm  yield  boat preheated  number o f c o u n t s  d e t e r i o r a t i o n i n the  d proton  into films  Evaporation  a 0.318  through  atoms f r o m t h e  ethylene  nickel  after  r a t i o of the  from m e l t i n g o r s u b l i m a t i o n .  nA  decrease  the  p o s s i b l e t o d e t e c t any  resulting  yield  deuterium  M.  i t was  beam o f 200 10%  about a  By m o n i t o r i n g  f o r measuring  absorbers  target.  using  In v i e w o f  measurements through t a r g e t , i t was  of such a t a r g e t .  decided  use to  heavy the of  a  investi-  62).  - 11 -  B o t h p o u r e d and e v a p o r a t e d Preliminary both  sides  study  indicated  l o s s o f a 690 were s t u d i e d  rapidly  3  He  keV H e  well The  decreased  alpha  o f kS  to prevent  as f o r 135  particle  f o r a 100  keV e n e r g y >  2  yield  integrated  as t o compare t h e r e l a t i v e two p r o c e d u r e s w e r e a l s o  3  He  beam c u r r e n t  f i l m s were s u b j e c t e d  ening  of the targets  polymer  of films,  t o gamma  of pouring  2  loss  H ( He,p) He, as 3  tf  i n c i d e n t on t h e t a r g e t . of the target  samples as  and e v a p o r a t i n g  aspects  ^Dt^n.  such as  thickness  and e a s e o f p r e p a r a t i o n .  Some o f  r a d i a t i o n to t e s t the p o s s i b l e  through " c r o s s - l i n k i n g " (see s e c t i o n  2.2.k)  strengthof the  chains.  The h o r i z o n t a l a n d v e r t i c a l measured.  This  copper backing  was  from the target from  The  thicknesses  total  profiles  target  l o s s o f an  of the associated  proton  c a r r i e d o u t t o o b s e r v e t o what e x t e n t  protons emerging  energy  merits  films  r e f l e c t e d by a  from the r e a c t i o n  compared f o r o t h e r  strength  The t h i c k e r  l o s s was  onto  destroyed  f i l m s were  yg/cm .  The d e u t e r i u m  layers  from being  compensate f o r t h e deuterium  targets.  studied.  Polyethylene  (as r e q u i r e d  2  carbon  the f i l m  densities.  yg/cm  t e c h n i q u e s were  of evaporating  y i e l d s were measured t o t e s t t h e u n i f o r m i t y  accuracy, mechanical the  film  t o see i f they would  in the thinner  production  the necessity  beam) a s w e l l  3  a f u n c t i o n o f the t o t a l Alpha  t t  beam c u r r e n t  f o r a thickness  observed  2  of the polyethylene  under the r e q u i r e d studied  (C D )n f i l m  had r e d u c e d  the s e l f - s u p p o r t i n g  i n yg/cm  incident proton  2  the e l a s t i c  beam w e r e  removal  of the  s c a t t e r i n g of the  target.  were c a l c u l a t e d  beam a t a g i v e n  from the measured  energy.  - 12 -  Finally, either  i t was d e c i d e d  s i d e o f the (C^DiJn f i l m  performance, as regards a  3  He  to vary  beam.  the t h i c k n e s s o f the carbon and t o o b s e r v e  alpha y i e l d  l a y e r s on  t h e e f f e c t on t h e t a r g e t  and d e u t e r i u m  l o s s , when e x p o s e d t o  - 13 -  CHAPTER  I I  EXPERIMENTAL METHOD AND  2.1  General  Preliminary  DESIGN  Introduction  tests  indicated  that  (C^tjn  a self-supporting  destroyed  immediately a f t e r exposure t o the He  beam.  10 y g / c m  t h i c k carbon  side  3  2  l a y e r o n t o one o r o t h e r  was n o t e f f e c t i v e i n p r e v e n t i n g  destruction  targets  the required  capable of withstanding  obtained of  by e v a p o r a t i n g  the (C Di )n 2  target  film  +  Chapter  II i s f i r s t  targets  by b o t h 2  4  technique  pouring  and e v a p o r a t i n g  l a y e r and t h e carbon  During  2  evaporated served  (C D )n 2  t t  films  to ascertain  I t was u s e d (approximately  the thickness  mentioned evaporated  (C D )n  targets  thick)  (^132  yg/cm  onto the thinner  beam c u r r e n t layers  2  2  2  targets.  L f  "sandwich"  of the "sandwich"  The t h i c k n e s s  1 +  o f both  whose  (C DL )n 2  thickness  f  resonator  t o measure t h e t h i c k n e s s 132  yg/cm  2  thick).  was thickness of  In a d d i t i o n i t  o f t h e c a r b o n f i l m s f o r t h e above  targets  as w e l l  as f o r t h e poured  and f o r a d d i t i o n a l There  sides  description of  of this  the (C D )n.  film  d e n s i t i e s were  onto both  the preparation  t  Stable  Hence a l l f u r t h e r  the course o f t h e work a q u a r t z  m o n i t o r became a v a i l a b l e .  2  l a y e r s was d e t e r m i n e d by a w e i g h i n g  f o r those "sandwich" targets  yg/cm .  of the (C Di )n  the preparation  o f a l l concerned with  was  Evaporation of a  of the target.  t h i c k carbon  i s concerned with  target.  (C Di )n  2  ("sandwich" t a r g e t s ) .  preparation  type of  the  10 y g / c m  film  layers  is also a discussion  of carbon  (C DLf)n 2  evaporated  of the possible  - H -  strengthening of the t a r g e t through r a d i a t i o n exposure  This chapter  gamma r a d i a t i o n  used.  t h e n d e s c r i b e s how t h e v a r i o u s c h a r a c t e r i s t i c s o f t h e " s a n d w i c h "  t a r g e t s were a s s e s s e d  in relation  i  to the reaction  means o f a s s e s s m e n t w e r e a l p h a y i e l d e v a l u a t i o n v i a the energy beam p r o f i l e  loss  Target Preparation  2.2.1  C a l i b r a t i o n of Thickness  A S l o a n DTM-3 (SI 69) films  oscillators. evaluating  film any  Monitor The t h i c k n e s s o f t h i n  t h e f r e q u e n c i e s o f two d i f f e r e n t  t h e mass o f t h e d e p o s i t i s m e a s u r e d by  up on i t s s u r f a c e . i s tuned  oscillator  i n a beat  the e m p i r i c a l material  t o each  so t h a t t h e "beat  i s zero.  frequency  equation  Prior  f r e q u e n c y " between i t  An i n c r e a s e i n t h e mass o f t h e c r y s t a l  change.  T - 2Af/p  The f r e q u e n c y  shift  thickness (using t h i s monitor) necessary  With  The e s t i m a t e d  on an a d j a c e n t s u b s t r a t e must  i n the monitor  locations o f the monitor  evaporation source.  A f i s g i v e n by  (where T i s t h e t h i c k n e s s i n A° o f a.  3  corrections  as t h e  evaporation a variable  o f b u l k d e n s i t y p ( g / c m ) and Af i s i n c y c l e s / s e c ) .  geometrical  The  t h e change i n f r e q u e n c y o f a r e s o n a t i n g q u a r t z c r y s t a l  the c r y s t a l result  3  i n t h e t a r g e t o f a p r o t o n beam, and p r o t o n  i s m e a s u r e d by c o m p a r i n g  frequency o s c i l l a t o r  will  H( He,p)^He.  measurements, t a r g e t t h i c k n e s s  t h i c k n e s s m o n i t o r was u s e d .  Specifically,  deposit builds  and  2  measurements.  2.2  evaporated  and t h e method o f  T v a l u e due t o p o s s i b l e  head a n d s u b s t r a t e r e l a t i v e  our equipment  i t was f o u n d  include; different to the  more c o n v e n i e n t t o  - 15 -  calibrate  the T monitor  s e p a r a t e l y f o r both  c a r b o n and p o l y e t h y l e n e  evaporations.  Calibration  was a c c o m p l i s h e d  a microgram  balance, then e v a p o r a t i n g the d e s i r e d  slides from  by f i r s t  and r e w e i g h i n g t h e g l a s s s l i d e s .  shift  per yg/cm  calibration 2  i n terms  reduce  the r e l a t i v e e r r o r  (resulting  from ambient  configurations  and  was e v a p o r a t e d  ( s e e F i g u r e s h and 6), carbon  of the frequency by w e i g h i n g )  A sizable  shift  resulted  amount  (of the  f o r the c a l i b r a t i o n  to  i n t r o d u c e d by t h e b a l a n c e ,  h u m i d i t y changes e t c . ) .  2  on  substance onto the  (measured  slide.  in the weighing  c y c l e s / s e c per yg/cm for  film  used  slides  o f t h e number o f c y c l e s / s e c f r e q u e n c y  f i l m t h i c k n e s s on e a c h  o r d e r o f 1 mg on a 1" x 3" s l i d e )  1" x 3" g l a s s  A comparison  the monitor with the thickness of films  in a T monitor  19.90  preweighing  With  the experimental  the c a l i b r a t i o n  f o r carbon  was  f i l m t h i c k n e s s on t h e c e n t r e s l i d e ,  (C2Dtt)n t h e c a l i b r a t i o n was 9.83 c y c l e s / s e c p e r y g / c m  (CzDi^n  2  t h i c k n e s s on t h e 2 c e n t r e s l i d e s .  The h i g h t e m p e r a t u r e evaporation, resulted  o f the carbon i n thermal  r o d s and c o n t a c t p o i n t u s e d  shock  on t h e o s c i l l a t o r c r y s t a l  (C2 it)n f i l m s w e r e i n d a n g e r o f b e i n g damaged. n  reduced (i)  by t h e f o l l o w i n g  The h e a t  t h e e l e c t r i c power d i s s i p a t e d  allowing Figure  4.  and t h e  radiation  was  steps:  The s i z e o f t h e c o n t a c t p o i n t o f t h e c a r b o n limit  i n the  the carbon  r o d s was  reduced  to  to the contact region thereby  t o e v a p o r a t e a t a much l o w e r c u r r e n t v i z :  -  (ii) A  tantalum shield  only (iii)  the a r e a about  W a t e r c o o l i n g was and  88%  near  mount was -  the face of  shock  thickness  no  occurred used,  2  t h e two  f  the heat  each  i t was  duce f i l m s o f  t t  to a T monitor  of  t h e amount o f  weighed time.  the d e s i r e d  (C D[ )n evaporated +  frequency  calibration  error  determined  f o r the  grain  2  +  mounted  shift  evaporated  calibration  The by  that  the return  the  monitor  final  was  the  possible  and  before) equipment  unless the  t h e amount o f  (C Di )n t  estimated  t h e measured  by This  (as e x p l a i n e d With  a  source"  determined  evaporation of  2  case  box  r e q u i r e d to  sample (C D )n 2  frequency  shift.  be  t +  pro-  thickness of  (C Di )n evaporation i s estimated to 2  [ +  evaporation.  f o r the monitor.  t h e amount o f  thickness.  f i l m was  such  was  2  after  s i n c e complete  possible to calculate  (C D )n.]  In t h i s  the " s i n g l e  b e f o r e and  2  From t h e m o n i t o r  the  (SI 6 9 ) ] .  from  (C Dif)n  beforehand,  on  (of the type where  t h i c k n e s s i n yg/cm  1" x 3" g l a s s s l i d e s  holders  s h i e l d was  i n a s i m i l a r way.  evaporated 2  rod  including  radiation  the c r y s t a l  done  leaving  crystal.  in a thickness c a l i b r a t i o n  control  cooling  t o 15 s e c o n d s ) d i d n o t e f f e c t  (C D )n  The  corresponded  t h e amount was  The  by  i n 10  ( C D i ) n was  2.2.3).  resulted  used,  2  experienced  state occurs  amount o f  weighing  [Note: water  [ a s e x p l a i n e d i n t h e S l o a n manual  (see s e c t i o n  and  reduced  p o l y e t h y l e n e c a l i b r a t i o n was  given  the carbon  for a l l evaporation  the q u a r t z  thermal  The  mount.  rods  exposed,  t r a n s m i s s i o n t u n g s t e n mesh r a d i a t i o n  small  accuracy  the c o n t a c t p o i n t  used  improvements a d e q u a t e l y  the normal  the carbon  i n c o r p o r a t e d i n t o both  These  to  p l a c e d around  the quartz c r y s t a l  crystal ( i v ) An  was  16 -  each :  3.0" 4.6"  to  T Moni t o r  to  3 -  3"  x  1"  SI i d e s  Cutaway of Tanta1um S h i e l d Over C a r b o n Rods  Current  Spect r o s c o p i ca11y P u r e C a r b o n Rods  Narrow Reduce  FIGURE  4:  GEOMETRY  Groove to Lateral Sliding  OF  CARBON  EVAPORATION  APPARATUS  - 18 -  t  8.7% a n d i s composed o f t h e f o l l o w i n g : a)  A w e i g h i n g e r r o r o f 2.5% due t o a s l o w d r i f t the  m i c r o b a l a n c e when w e i g h i n g  the s l i d e s ,  e x p e r i e n c e d by  r e s u l t i n g from  h u m i d i t y changes e t c . b)  A monitor error  consisting of a ± 7 cycles/sec  e r r o r and a r e p r o d u c i b l e  the of  average thickness  The  total  of  uncertainty  f o r each s l i d e  o f t h e sum o f t h e s q u a r e s  errors.  as above e x c e p t t h a t  in a total  2.2.2 To  error  reproducible  (as m e n t i o n e d  Poured P o l y e t h y l e n e  pared powdered  t t  to a further  accuracy plus  leaving  monitor  a - 7 cycle/sec  layer alone, a thin f i l m of  (De 69)  in a quantity  scale  t h e (C Dt )n f i l m . 2  (  polyethylene  of commercially  pre-  of b o i l i n g Xylene solvent.  s o l u t i o n was p o u r e d o n t o a 3 " x 3 " " p r o c e s s c l e a n " to evaporate  to the  Targets  d i s s o l v i n g a measured q u a n t i t y  (C D )n 2  In a d d i t i o n  5%>  before).  o b s e r v e and t e s t t h e (C^Di^n  was p r e p a r e d by f i r s t  i s composed  t h e w e i g h i n g e r r o r was ±  c a l i b r a t i o n e r r o r o f - S.6%.  composed o f a i 21  reading  from the  point).  c a l i b r a t i o n e r r o r s , al1 evaporations are subject error  from  (since a l l parts  i n the c a l i b r a t i o n f o r the carbon evaporation  t h e same e r r o r s  resulting  calculated  e r r o r was c h o s e n a s t h e s q u a r e r o o t  of a l l the possible The  v a r i a t i o n across the s l i d e  t h e s l i d e a r e n o t a t t h e same r a d i a l d i s t a n c e  evaporation  reading  a c c u r a c y o f t 2%.  An e r r o r o f 8% due t o t h i c k n e s s  c)  scale  s l i d e enabling  After preliminary  The  the Xylene  testing a  - 19 -  c o n c e n t r a t i o n o f 41.0 of t  X y l e n e ] was 25%  (this  i n 30 ml o f X y l e n e  t o produce  o f 25  slides (C2Di )n  large area  t  of  t h i c k n e s s m o n i t o r was  t h e c a r b o n and  weighing.  The  in F i g u r e  5-  A carbon of  yg/cm  f i g u r e o f 10  f o r a 690  f i l m was  day  yg/cm  2  The  cm)  t e s t was  to  from the s l i d e s  to  (C D )n t a r g e t 2  )+  "sandwiches", layer  thick-  n e c e s s a r y t o d e r i v e a t e c h n i q u e whereby the t h i c k n e s s  be t h i c k e n o u g h t o g i v e s t a b l e  a s i d e f o r one  t h i c k n e s s o f 44  p o l y e t h y l e n e l a y e r s c o u l d be d e t e r m i n e d  The  +  not a v a i l a b l e t o measure the c a r b o n  l a y e r o f a p p r o x i m a t e l y 10  loss  2  slide.  thick  2  ( C D i ) n p e r ml  t h e above c o n c e n t r a t i o n  x 2.5  cm  g e o m e t r i c e v a p o r a t i o n and  the s l i d e .  energy  (2.5  sections  mg  T h i s t h i c k n e s s and  a t by t e s t i n g  t h i c k n e s s f o r each  Hence i t was  film  from 5 s e p a r a t e p o u r i n g s .  D u r i n g p r e p a r a t i o n o f t h e 44  nesses.  1.36  [ie  3.2).  is discussed in section  a r r i v e a t an a v e r a g e  the  an a v e r a g e  f i g u r e were a r r i v e d  over a t o t a l weigh  found  error  uncertainty  mg  keV  3  He  yg/cm  yg/cm  pouring technique is  is first  2  was  2  chosen  because  (see Appendix  to enable the carbon  layers  then prepared over the whole s l i d e ,  B).  rise The  to harden. including  by  illustrated  evaporated over  targets, while giving beam  separately  part  i t appeared  to  t o o n l y 18.8  keV  s l i d e s were s e t The p o l y e t h y l e n e  t h e c a r b o n a r e a , as  fo11ows: (i)  The  measured q u a n t i t y o f  containing (ii)  The  30  ml  s o l u t i o n was  poured  ( C D ) n was 2  of b o i l i n g  (+  x 3"  ml  beaker  Xylene.  lightly boiled  i n t o t h e 3"  p l a c e d i n a 50  f o r at  glass slide.  ; l e a s t 5 minutes The  quality  and  of the  then (C D )n 2  ( +  Step  — r — | — • -  A.  'X_LO. T^I_PJ_XTO|X. TT | 01 X | o T x _ | 0 ToTx_j_p  i  1  1  i  1 |_l_ 1 i 1 f. 1 1 1 c ir H• -i rJ_[_L: A H - h  c)  d)  Note:  FIGURE  5:  Weighing Procedure: a) Weigh samples from s e c t i o n A , average gives ^ polyethylene thickness b) W e i g h s a m p l e s f r o m s e c t i o n B, a v e r a g e g i v e s ^ ( p o l y + 1st c a r b o n l a y e r ) a n d s u b t r a c t i n g a ) we h a v e ^ 1st c a r b o n t h i c k n e s s  In s e c t i o n D, X ' s i n d i c a t e t h o s e s a m p l e s which are weighed to determine thickn e s s , and O ' s i n d i c a t e those samples t o be u s e d f o r t h e e x p e r i m e n t .  SELECTIVE  EVAPORATION,  PROCEDURE  FOR k$  y  Similarily, section C gives, ^ ( p o l y + 2nd c a r b o n l a y e r ) a n d t h e r e f o r e ^ 2nd c a r b o n layer S e c t i o n D g i v e s ^ ( p o l y + 1st c a r b o n + 2nd c a r b o n t o t a l thickn e s s ) a n d by s u b t r a c t i n g b) a n d c ) we h a v e ^ p o l y t h i c k n e s s .  q/cm  POURING 2  THICK  AND W E I G H I N G POURED  (C Di»)n 2  TARGETS  - 21 -  films obtained i s extremely s e n s i t i v e self. to  I t was  slide  tilt  until  about  hard  The b e a k e r was  constant rate.  from  slide.  Usually  solution  motion  (ie  2 ml p e r s l i d e ) .  o f f the glass  an a n g l e o f 30° scraping the water  The  than  the carbon  2  requiring  20 ml o f  10 ml o f  solution  of the s o l u t i o n  resulted  i n (C Di )n  t h i c k n e s s was  then s c r i b e d  1 cm x 1 cm.  2  then evaporated  +  The v a r i o u s f i l m  surface.  Lift  slowly  the f i l m  begins  (C D[ )n 2  +  to l i f t .  layers  tool)  off is facilitated  by  edge t o j u s t lift  require a patient  and  into  were  lukewarm w a t e r  Polyethylene films  but both  5.  combinations  into  this  onto the  in Figure  (using a sharp c u t t i n g  by l o w e r i n g t h e s l i d e  to the water  plus  1.5  remaining  t h e edge o f t h e s l i d e a n d t h e n a l l o w i n g until  motion i s  on t h e w a l l s o f t h e b e a k e r .  The s u r f a c e o f t h e s l i d e was  floated  at a  i t took approximately  10 s l i d e s w e r e p r e p a r e d  l a y e r o f 10 y g / c m  size  at a constant  o f the sweeping  p o l y e t h y l e n e f i l m o v e r p a r t o f the s l i d e as i l l u s t r a t e d  of square  across the s l i d e .  t h e b e g i n n i n g t o t h e end o f t h e sweep a c r o s s t h e  precipitating  a grid  to  glass  pouring out o f the beaker  The s p e e d  d i s c a r d e d because c o o l i n g  carbon  The method was  then swept d i a g o n a l l y  t o measure but t h e a u t h o r found  seconds  necessary  began t o p o u r j u s t o u t s i d e t h e edge o f  and t h e f l u x o f s o l u t i o n  relatively  were  1" a b o v e t h e h o r i z o n t a l  i s important t o m a i n t a i n the sweeping  speed  A second  the beaker  the s o l u t i o n  the s l i d e .  was  t h a t a l a r g e number o f t r i a l s  d e v e l o p a s t a n d a r d i s e d p o u r i n g method.  gradually  It  found  t o the pouring motion i t -  at  first touch easier steady  - 22 -  hand.  As  a r e s u l t of the s e p a r a t e samples of  c a r b o n , we w e r e a b l e t o d e t e r m i n e a v e r a g e  ( C ^ D ^ n and  t h i c k n e s s of the v a r i o u s l a y e r s  by w e i g h i n g t h e s a m p l e s as d e s c r i b e d i n F i g u r e 5.  The  targets  experiment were taken from s e c t i o n D o f the lower s l i d e ( s t e p k).  A l t e r n a t e samples were chosen  the samples average  from the g r i d  o f the measured samples about  them.  h o l d e r s w i t h 0.25  with  When t h i s w o r k was  yg/cm  2  p r e p a r i n g and In t h i s slide,  (C D( )n p o u r e d 2  testing  2  f i l m had  a grid  t h e 135  yg/cm  carbon  l+  a second  carbon  r o u g h l y 10%.  like  t h e one  s t e p 4 i n F i g u r e 5).  and  statistical  i n the  f l a t metal  (copper)  the h o l d e r s were  affected.  targets  t h i c k n e s s e s when  selection  The  reason f o r 1.3.  is discussed in section  carbon  l a y e r as d e s c r i b e d  to e s t i m a t e the carbon  [+  procedure  layer thickness  determined  as o u t l i n e d  by  scribing  then u t i l i z i n g  more a c c u r a t e t h i c k n e s s e s t i m a t i o n s f o r t h e t o t a l yields  a  f o r s e c t i o n D (of  T h i s '"sandwich" t a r g e t p r o d u c t i o n p r o c e s s g i v e s  t h e T m o n i t o r and  3"  x  evaporated over the p o l y e t h y l e n e .  ( C D ) n t h i c k n e s s was 2  layer  became  e v a p o r a t e d o v e r t h e w h o l e 3"  over t h i s  l a y e r was  The  2  l a y e r was  formed  carbon  i n F i g u r e 5 o n t o t h e w h o l e s l i d e and  s t a g g e r e d w e i g h i n g and  without  used  t a r g e t s were p r e p a r e d .  +  m o n i t o r c a l i b r a t i o n e n a b l e d one  to w i t h i n  been  t o m e a s u r e t h e two  ( C D ) n f i l m was  b e f o r e and The  thick  case the f i r s t the  on a  a l r e a d y i n p r o g r e s s , the t h i c k n e s s monitor used  figure  raised slowly at a steep angle a f t e r contact  t h e edge o f a f l o a t i n g  t h e 132  s u r f a c e on  in the  t o be w e i g h e d  targets  i n c h d i a m e t e r h o l e s as f o l l o w s :  i n t o t h e w a t e r and  a v a i l a b l e and was  The  used  in the  i n t e n d e d f o r use were a s s i g n e d a t h i c k n e s s based  e x p e r i m e n t w e r e p i c k e d up f r o m t h e w a t e r  dipped  (C^Di^n p l u s  15%  t h i c k n e s s than the p r o c e s s  a g r e a t e r number o f u s a b l e t a r g e t s  per  - 23 -  slide  (up t o t h r e e t i m e s a s many)•  2.2.3  Evaporated  Polyethylene Targets  P r e l i m i n a r y a t t e m p t s a t e v a p o r a t i n g (C Di )n 2  different  sizes  and s h a p e s  t a i n i n g what a p p e a r e d  produced  t o be s m a l l  f i l m s o f a g r a n u l a r appearance,  pieces of solid  Some powder g r a i n s seem t o be e j e c t e d complete  evaporation.  eliminate this  A baffle  source  is illustrated  fed v i a the d e l i v e r y The  b a f f l e system  current through  the e n t i r e  The  the f i r s t  v a p o r i z e d from r e a c h i n g  to suffer multiple collisions with i n a steady p a r t i c l e - f r e e  D e l i v e r y o f t h e (CgDi^n  because  thematerial  The t e c h n i q u e . w a s  vapor  into the hot  t o adhere  to the  c h a n g e d and a w e i g h e d  quantity  T h e f u n n e l was  t o p r e v e n t any p o s s i b l e e v a p o r a t i o n t h r o u g h i t s 2  minute.  tended  box v i a t h e f u n n e l .  T h e r e q u i r e d amount o f (C Di )n  b o x was t h e n h e a t e d  within  temperature.  length of the u n i t , prevents condensation of  was d e p o s i t e d i n t h e c o l d  s e a l e d w i t h aluminum f o i l opening.  This results  t o be e v a p o r a t e d i s  kept a t t h e d e s i r e d  not f u l l y  the material  b e t w e e n f u n n e l and c h i m n e y .  w a l l s o f t h e warm f u n n e l . +  The m a t e r i a l  system.  U n i f o r m h e a t i n g o f t h e s o u r c e o b t a i n e d by p a s s i n g  s o u r c e had t o be e l i m i n a t e d  2  (Ma 69) i n c o r p o r a t e s s u c h a b a f f l e  p r e v e n t s any m a t e r i a l  stream a t the e x i t .  (C Di )n  i n them  s y s t e m n e a r t h e s o u r c e was n e c e s s a r y t o  f u n n e l i n t o t h e "box"  the h o t w a l l s o f t h e "box".  of  imbedded  from t h e hot boat s u r f a c e s b e f o r e  i n F i g u r e 6.  t h e e x i t c h i m n e y by f o r c i n g  material  material  con-  effect.  A " S i n g l e G r a i n Box S o u r c e " The  from open t a n t a l u m b o a t s o f  t  up t o o290°C r  +  was d e t e r m i n e d  a s d e s c r i b e d i n 2.2  (Wh 65) a n d e v a p o r a t i o n was c o m p l e t e d  Due t o t h e l o w e v a p o r a t i n g t e m p e r a t u r e  for  (C2^k)  - 2k -  2.3"  Delivery  t o 2 - 1" x 3" G l a s s S i i d e s  Funnel  E x i t Chimney Current  FIGURE 6:  the heat With the  SCHEMATIC DIAGRAM OF THE "SINGLE GRAIN  radiation  protection  two 1" x 3" g l a s s loss of evaporated  Using  the c a l i b r a t i o n  f o r the T monitor  s l i d e s mounted 2.3" d i r e c t l y material  into  procedure  As  yielded  i s not r e q u i r e d .  over the e x i t  chimney,  i n 2 . 2 . 1 , i t was f o u n d  a film  that  t h i c k n e s s o f ^135  yg/cm  2  slides.  i n the pouring t e c h n i q u e , a carbon  t h i c k n e s s was f i r s t l a y e r o f ^135 yg/cm layer.  SOURCE"  t h e vacuum c h a m b e r e t c , was v e r y h i g h .  as o u t l i n e d  e v a p o r a t i o n o f 16.0 mg o f ^ D i j n o v e r t h e two  crystal  BOX  evaporated onto 2  thick  The s t r i p p i n g ,  layer of approximately  the glass  ( C D i ) n and f i n a l l y 2  floating  t  slides  10 y g / c m  2  f o l l o w e d by an e v a p o r a t e d  a second  10 y g / c m  2  carbon  and p i c k - u p p r o c e d u r e s were c a r r i e d  out i n  -  the  25  -  same way a s f o r t h e p o u r e d " s a n d w i c h "  These t a r g e t s were m e c h a n i c a l l y weaker than to  a large f a i l u r e  2.2.H  Target  There  i s evidence  chains, of  t h e polymer c h a i n s . i s indicated  h u n d r e d s o f C ®h  The  strengthens  close proximity. interaction scattering.  they  This  interaction  atom H .  The s e c o n d a r y  linked  The r e s u l t i n g  ening  polymer chains  large  atoms o f d i f f e r e n t the substance  The s e c o n d a r y  i n Figure  H*  molecular  i s Compton  bond  until  (ofthe order o f  a heavy  hydrogen  i t t o break t h e  ( i e k i n e t i c e n e r g y >KT). T h i s  left  without  t h e c h a i n , o r between a d j a c e n t  chains  H* may  i t t o break  i'ts H a t o m s , f o r m s a  T h i s may o c c u r w i t h i n t h e p o l y m e r c h a i n thereby  through  secondary  e l e c t r o n s lose energy  H atoms c a u s i n g  7.  the predominant  20 t o 3 0 , 0 0 0  the H causing  occur  chains are i n  the substance  use H t o s i g n i f y  electron strikes  C-C p a i r ,  "cross-1inking"  t h e degree o f p o l y -  t o g e t h e r as i l l u s t r a t e d  i n t e r a c t w i t h one o f t h e a d j a c e n t  bond C=C.  through  produces high energy e l e c t r o n s which,  d i s c u s s i o n we w i l l  C-H bond a n d l e a v e a s a " h o t "  bond.  f  t h e r e s o n a n c e e n e r g y o f t h e C-H c h e m i c a l  For this  then  2  g i v e use t o approximately  10 e V ) . 2  (C Di )n  (relevant to cross-1inking) with  ("cascade" e f f e c t ) .  reach  the substance  When a gamma r a y e n t e r s  collisions,  electrons  composed o f p o l y m e r  by t h e s u b s c r i p t n a n d n o r m a l  c h a i n s a r e i n t e r c r o s s e d and d e u t e r i u m  multiple  a substance,  o f c r o s s - 1 i n k i n g i s p o s s i b l e because these  process  rise  and p i c k - u p .  For the substance  molecules  2  t h e poured ones, g i v i n g  Through R a d i a t i o n  (Pr. 67) t h a t e x p o s i n g  t o gamma r a d i a t i o n  merization as  rate during stripping  Strengthening  (see s e c t i o n 2 . 2 . 2 ) .  targets  itself,  double  thereby  b i n d i n g them  i t s C-H  strength-  together.  - 26 -  H = D (Heavy H y d r o g e n ) H*= " H o t " H y d r o g e n  Note: Compton  A  Scattering ^  H  H  H  H  H  I  Y Ray  <+• m e  - C  -  C  C  C -  •  I  .e  •H^JTH  H  H  H  _  Cascade  H+H* H'  H  »e -  Energy ^e Electron  \  |Jyp i c a 1 Polymer Chai n  Effect  /  RESULT  C  -  C  -  C  H  -  C  -  C  -  C  -  I  I  I  I  I  I '  H  H  H  H  H  H  H  H  H  H  H  H  4he  C  -  C  -  D o u b l e Bond Chain Strengthening H  H  C  -  -  H  H  H  c H  SCHEMATIC DIAGRAM OF STRENGTHENING  C  H  he  FIGURE 7:  H  H  H  H  POLYMER  THROUGH GAMMA RADIATION  C  -  Double -Bond "CrossLinking"  -  c H  - 27 -  The  latter  case  i s known a s " c r o s s - 1 i n k i n g " .  to s t r e n g t h e n the m a t e r i a l , " c r o s s - l i n k i n g "  As m e n t i o n e d  before  (2.2.3)  Although i s more  2  +  were m e c h a n i c a l l y weaker than the poured  ones.  decided  (while s t i l l  targets  t o a s u s t a i n e d d o s e o f gamma r a d i a t i o n by  this  radiation  technique.  I t was  current  Two  "sandwich"  target  (C2 it)n t h i c k n e s s a p p r o x i m a t e l y e q u a l n  o f 3 and taining  12  MegaRads.  6170  curies of  2.3  Alpha Y i e l d  2.3-1  Method  As  The 6 0  2  was  deuterium of  i t was  t o t h e 690  keV  3  He  l o s s e s as w e l l  Consequently  alpha y i e l d  were exposed  2  field  beam  to  200"  \ doses  con-<  o f hkkO R a d s / m i n .  i s given  t o a s s e s s the performance  beam.  One  integrated  3  He  the t a r g e t  from  the  reaction  beam c u r r e n t on deterioration  as p r o v i d i n g an e s t i m a t e o f t h e d e u t e r i u m  t i m e d u r i n g He 3  after  t h e t a r g e t has  the deuterium i n terms  bombardment.  I t i s not c l e a r  b e e n bombarded by  c o n t e n t a t any  of  o f t h e means o f  (in counts/yc)  T h i s p r o v i d e d a means o f m e a s u r i n g  the deuterium e x i s t s  3.3.1).  target  h a v i n g an e v a p o r a t e d  yg/cm  necessary  t o measure the a l p h a y i e l d  t h e t a r g e t s a t any  form  slides  producing a radiation  4  target.  improvements  t o w i t h s t a n d g r e a t e r 3He  t o 135  H ( H e , p ) H e , as a f u n c t i o n o f t h e t o t a l 3  resulting  slides)  Measurements  t h e t a r g e t s when e x p o s e d assessment  the g l a s s  s l i d e s were p l a c e d i n a "Gammacell  C o and  i n s e c t i o n 2.1  mentioned  on  targets i t was  hoped t h a t t h e p o s s i b l e  a l s o permit the t a r g e t s  densities.  Consequently  t o c o m p a r e any  s t r e n g t h e n i n g might  serve  effective.  (C Di )n " s a n d w i c h "  the evaporated  t o expose the evaporated  both cases  3  through  content i n what  He.(see  point determined  from  o f an " e q u i v a l e n t p o l y e t h y l e n e t h i c k n e s s "  the  - 28 -  in yg/cm yield  The  3  i.e. t h a t  2  (C^DiJn  thickness  which would g i v e  ( f o r t h e H e beam u s e d ) as m e a s u r e d 3  H e beam was s l i g h t l y  The a l p h a  defocused so that  state detector.  p a r t i c l e s produced The a p p a r a t u s  t h e beam s t r i k i n g  time  detector)  intervals, f o r a preset  measured. yc  the t o t a l  i s described  amount o f e l e c t r i c  time that  the target  i n d i c a t i o n of the target targets  with  beam c u r r e n t s )  time.  currents  Usually  plotted  number o f H e 3  total  exposed  followed  i t was a s s u m e d t h a t  t o . The t o t a l  A  At  3  into, the  3  counts per  (where t i m e r e f e r s t o ; t h e  t o t h e beam).  i n the alpha  by a s l o w  This  g a v e an  yield  (more  rapid  ( e s s e n t i a l l y l i n e a r ) decrease f o r o n e h o u r a n d beam  and d i f f e r e n t t a r g e t  spots) varied  from  yA.  d e t e r i o r a t i o n from d i f f e r e n t samples and this  traversing the target.  function of the total  t o t h e H e beam.  most m e a s u r e m e n t s c a r r i e d o u t a t 0.1  number o f a l p h a  solid  i n t h e H e beam was  beam c u r r e n t  rapid decrease  t o compare t h e t a r g e t  beam s p o t s ,  in a  d e t e r i o r a t i o n u n d e r d i f f e r e n t beam c u r r e n t s . A l l  (for different targets  In o r d e r  t h e beam  i n s e c t i o n 2.3-2.  i n the form o f alpha  measurements were c o n t i n u e d  0.05 yA t o 2.0 yA w i t h  across  p a r t i c l e s (emitted  charge  had been e x p o s e d  e x h i b i t e d an i n i t i a l  for higher  the  s p o t was e x p o s e d  as a f u n c t i o n o f time f o r a g i v e n  total  in detail  number o f a l p h a  The r e s u l t s w e r e f i r s t  density  the target  i n t h e t a r g e t were d e t e c t e d  c l o c k was s t a r t e d when a new t a r g e t fixed  alpha  (see Appendix C ) .  ( v i a a c o l l i m a t o r a s s e m b l y ) had a u n i f o r m c u r r e n t spot.  t h e same  e f f e c t i s a function of the total The c o m p a r i s o n was e f f e c t e d  p a r t i c l e s detected  i n c i d e n t charge that integrated  current  f o r a given  by p l o t t i n g  c h a r g e as a  a p a r t i c u l a r beam s p o t h a d b e e n o n t a r g e t was c a l c u l a t e d by  - 29 \  multiplying  t h e beam c u r r e n t  a t each a l p h a (described 200  count measurement.  in greater  uc t o t a l  with  detail  the elapsed The  r e s u l t i n g alpha  in section  c h a r g e on t a r g e t .  time o f t a r g e t  3.3-0  yield  yield  a n a l y s i s and c o m p a r i s o n s were c a r r i e d o u t a t a t o t a l o f 300  on t a r g e t  Alpha y i e l d  y c a n d t h i s was  defined  measurements were f i r s t  w h i c h had a p o u r e d  curves  a f t e r 150  stabilized  Hence f o r a l l a l p h a  exposure  measurements,  integrated  as t h e " f i n a l  alpha  current  (^He)  c a r r i e d o u t on t h e " s a n d w i c h " o f ^hk  (CgDiJn t h i c k n e s s  yg/cm .  to  yield".  targets  These samples were  2  compared as f o l l o w s : (i)  T e s t s w e r e c a r r i e d o u t on d i f f e r e n t beam s p o t s sample t o measure p o s s i b l e t a r g e t diameter self-supported  (ii)  v a r i a t i o n across  (iii)  t o measure t a r g e t  v a r i a t i o n s across  T e s t s w e r e c a r r i e d o u t on t a r g e t observe the target  0.25"  the  s a m p l e s f r o m t h e same the s l i d e .  samples from d i f f e r e n t s l i d e s t o  v a r i a t i o n s from s l i d e  to slide.  Alpha y i e l d  m e a s u r e m e n t s w e r e c a r r i e d o u t on " s a n d w i c h " t a r g e t s o f  ^132  yg/cm  (C D( )n t h i c k n e s s ,  the  (C Di+)n.  2  2  2  pouring  +  This  was  prepared  by b o t h e v a p o r a t i n g  done t o c o m p a r e t h e m e r i t s  the (C Di )n  as r e g a r d s  to " f i n a l  The c h a n g e i n a l p h a  y i e l d with  d i f f e r e n t carbon  2  +  " s a n d w i c h " t a r g e t was poured the  (C Di )n 2  t  same s l i d e  targets  studied. o f ^kk  target  region.  T e s t s w e r e c a r r i e d o u t on d i f f e r e n t t a r g e t slide  o f t h e same  alpha  The m a j o r i t y yg/cm  2  and  pouring  of evaporating  and  yield".  layer thicknesses  on t h e  o f t e s t s w e r e c a r r i e d o u t on  thickness.  The t a r g e t s w e r e t a k e n  t o e n s u r e comparisons between s i m i l a r t a r g e t s .  I t was  from  - 30 -  possible was  to  first  t o t h r e e d i f f e r e n t s p o t s per  subjected  sistency target  t e s t up  t o an  alpha y i e l d  between t a r g e t s .  (while  on  the  After  target  different  spot.  10  thick evaporated  The of  yg/cm  2  target the  alpha y i e l d  target  incident  (ie  beam) as  sandwich c o n s t r u c t i o n  of  on the  ments f o r a g i v e n number o f were performed w i t h the  target  for  t o t a l s of  o p p o s i t e t o the  t h r e e and carried  four  out  s a m p l e was  2.3-2  8  one  the  target  targets,  a  "sandwich" targets  10  yg/cm  (on  in  on  from  Due  to  2  the  "back"  the the  alpha y i e l d  l a y e r on  the  basic measure-  side  T a r g e t s were on  the  t h i c k poured " b a c k " and  of  tested  " b a c k " and  A m e a s u r e m e n t was  yg/cm  the  e i t h e r "back" or " f r o n t " ) ,  layers  "front".  layers  the  layer side.  carbon  s a m p l e o f ^135  3 carbon  target.  t h i c k carbon  2  carbon  the  the  in a l l cases  four  on  l a y e r v a r i a t i o n on  sandwich f a r t h e s t  layers  of  i s a schematic drawing of beam l i n e s on  accelerator.  on  measured f o r  the  also  (C2Di )n.  This  +  3 on  one,  the  "front".  Apparatus  Figure  two  for  original  con-  evaporated onto  alpha y i e l d  " f r o n t " of  varied  layers  a target  tested  the  t h r e e and  carbon  on  the  carbon  a single  one, t w o ,  the  measured f o r carbon  as of  t h i s , more c a r b o n was  added o n t o the  side  well  target  layers.  was  the  Each  measurement to measure the  h o l d e r ) and  C a r b o n was  target.  sets the  of  A singly focusing  beam l i n e .  University  ionized  3  He  target of  beam was  chamber.  British directed  e l e c t r o s t a t i c q u a d r u p o l e s and  The  a s s e m b l y A w h i c h was  the  the  beam e n t e r e d  composed o f  two  the  C o l u m b i a Van to the steering  chamber t h r o u g h  defining  I t was  the  a p e r t u r e s and  attached de  to  Graaff  chamber v i a magnets mounted collimators a  skimmer  FIGURE  8.:.  SCHEMATIC  DIAGRAM  OF T H E  CHAMBER  SET-UP  FOR A L P H A Y I E L D  MEASUREMENTS  -  corresponding  t o a beam d i a m e t e r p f  32  -  0.160 cm (1/16").•"  i t s own v a c u u m p u m p i n g s y s t e m a n d was m a i n t a i n e d A f t e r passing  brass  through  t h e t a r g e t was s t o p p e d  electrons emitted assembly. Eldorado  T h e beam  E l e c t r o n i c s Model  (and i n s u l a t e d  t o repel  secondary  c o l l e c t e d by t h e F a r a d a y c a g e was f e d i n t o .an CI-110 c u r r e n t  i n t e g r a t o r ( E l 69).  i s presented  i n F i g u r e 9.  A bHock  The alpha  p r o d u c e d by t h e r e a c t i o n o f t h e H e beam o n t h e t a r g e t w e r e d e 3  t e c t e d by an Ortec r e s o l u t i o n , 750  Silicon  ft/cm)  surface barrier detector  (50 mm » 33 k e V 2  (Or 69) mounted o n t h e b a c k o f a c o l l i m a t o r *  i s part o f the s o l i d  The a n g u l a r  position with  respect  p o s i t i o n normal  F i g u r e 8 c a n be a d j u s t e d  without  t h e vacuum.  The  s i g n a l was f e d i n t o a c h a r g e s e n s 51 W e ,  109A  state detector  p r e a m p l i f i e r (Or 69).  breaking  totne  t o t n e p l a n e <8>ff  i n c i d e n t beam d i r e c t i o n , a n d t h e v e r t i c a l  solid  TUniis  s t a t e d e t e c t o r a s s e m b l y B w h i c h forums ipairtt  t h e chamber's bottom cover.  Ortec  A  from t h e back s u r f a c e o f t h e Faraday cage a n d t a r g e t  d i a g r a m o f t h e e l e c t r o n i c s used  detector  Torr.  5  i n a Faraday cage assembly C.  a t a p o t e n t i a l o f -300 v o l t s  T h e beam c u r r e n t  particles  D.  target holder  r i n g was m o u n t e d o n t h e f r o n t o f t h e F a r a d a y c a g e  from i t ) and maintained  of  a t a vacuum o f M O  t h r o u g h t h e c o l l i m a t o r s , t h e beam s t r u c k t h e s e l f - s u p p o r t i n g  t a r g e t w h i c h was m o u n t e d o n a w a t e r c o o l e d passing  The chamber had  F I T 5mf>umt„  The o u t p u t p u l s e o f t h e preawipliiffiier  was f e d i n t o a C . I . 1410 l i n e a r a m p l i f i e r (Ca 69) w i t h d i f f e r e n t i i a t i i < 0 m aroil i n t e g r a t i o n time constants S i n g l e Channel A n a l y z e r Ortec  430 S c a l e r  o f 1 us f o l l o w e d  (Ca 69).  (Or 69).  During  The o u t p u t  b y a C . I , 1^3$ T5ra»n§ §tlh f r o m t h e SCA w a s f e d i n t o am  t h e m e a s u r e m e n t s , t h e s e a l e r a n d tn©  -  33  REAMPLIFIER  -  FARADAY CAGE  S.S.D.  BIAS  LINEAR AMPLIFIER  SINGLE CHANNEL ANALYZER  CURRENT INTEGRATOR  OFF  KICKSORTER  ON  TRIGGER  SCALER  ON-OFF  TIMER  FIGURE  9:  BLOCK DIAGRAM THE A L P H A  OF  YIELD  THE  ELECTRONICS  MEASUREMENTS  FOR  - 3k -  current off  i n t e g r a t o r are switched  on m a n u a l l y .  a u t o m a t i c a l l y at a preset charge  a current  integration  of charge c o l l e c t e d  in the current  measurement o v e r / a  v i a the He  i s switched  integrator.  given period yields  beam a s w e l l  3  p a r t i c l e s o f a given energy c o l l e c t e d The o u t p u t  The s c a l e r  Hence,  the q u a n t i t y  a s t h e number o f a l p h a  by • t h e d e t e c t o r  i n t h e same p e r i o d .  f r o m t h e l i n e a r a m p l i f i e r was a l s o f e d i n t o a N u c l e a r  Multichannel  Pulse Height  Analyzer  (Nu 6 9 ) , w h e r e t h e s o l i d  Data  160  state detector  s p e c t r u m was  recorded.  As d i s c u s s e d  i n s e c t i o n 1.1, t h e k i n e m a t i c s o f t h e r e a c t i o n H ( H e , p ) H e 2  determine  the energies of the p a r t i c l e s  relative  t o t h e i n c i d e n t beam d i r e c t i o n .  detector w i l l ticles  determine  i n c i d e n t on  t h e mean e n e r g i e s  i t .  reduce t h i s  background  thick polyethylene. expected  scattered  covers  r e a c t i o n H ( He,p)^He. 2  angle  3  of the detector.  the protons  protons.  observed.  reduced  The e n e r g y o f t h e a l p h a s Particle  identification  to prevent  A similar  effect  par-  particles  b a c k g r o u n d due t o In o r d e r  lined with  in intensity,  available  detected  0.042"  a low  these from the  depends on t h e  i s necessary  t h e m e a s u r e m e n t o f an  c o u l d be p r o d u c e d  to  g r e a t e r than the  The e n e r g i e s o f  t h e r a n g e o f '•He e n e r g i e s  from the alphas  large alpha y i e l d .  still  and a l p h a  by t h e c h a m b e r w a l l s .  Although  of emission  of the alpha  and a l p h a  The p o l y e t h y l e n e t h i c k n e s s b e i n g  b a c k g r o u n d was  protons  protons  t h e i n s i d e o f t h e c h a m b e r was  r a n g e o f 16 MeV  energy proton  of the protons  a low e n e r g y p r o t o n  of the high energy protons  1+  f o r given angles  Hence t h e a n g l e  In a d d i t i o n t o t h e s e  o f d e f i n e d e n e r g i e s , t h e r e was scattering  emitted  3  to distinguish erroneously  from s l i t  edge  - 35 -  s c a t t e r i n g on t h e c o l l i m a t o r d e f i n i n g '•He d e t e c t o r .  The h i g h e n e r g y  grazing c o l l i s i o n s with  Particle  the s o l i d  protons would  angle subtended  be d e g r a d e d  i n energy  t h e c o l l i m a t o r on r o u t e t o t h e H e 4  such t h a t  ( =20 v o l t s  bias  depth f o r the  t h e maximum p r o t o n e n e r g y  much l o w e r t h a n t h e a l p h a e n e r g y o f i n t e r e s t . f o r t h e d e t e c t o r mentioned  during  detector.  i d e n t i f i c a t i o n was o b t a i n e d by c h o o s i n g a d e p l e t i o n  surface barrier detector  by t h e  d e t e c t a b l e was  A d e p t h o f 50 m i c r o n s  a b o v e ) was c h o s e n , c o r r e s p o n d i n g  t o a r a n g e o f 2 MeV p r o t o n s a n d 8 MeV a l p h a p a r t i c l e s  in silicon.  The  energy  in the solid  state .  spectrum as observed w i t h  d e t e c t o r would  this  d e p l e t i o n depth  t h e n c o n t a i n a s u p e r p o s i t i o n o f a p r o t o n and an a l p h a  spectrum: (i)  The p r o t o n s p e c t r u m  i s a d i s t r i b u t i o n which  (the " p r o t o n edge"). high energy  protons  I t a l s o has a peak, c o r r e s p o n d i n g t o t h e (^]k M e V ) , a p p e a r i n g a t l o w c h a n n e l s  t h e p r o t o n s go t h r o u g h t h e d e p l e t i o n d e p t h amount o f e n e r g y (ii)  detector angle  To e n s u r e  in the depletion  The a l p h a s p e c t r u m  that  is a single  t h e a l p h a peak w o u l d  it  A typical  illustrated  the alpha energy  solid  in Figure  leaving only a small  region.  peak w h o s e p o s i t i o n  be e a s i l y  f r o m t h e 2 MeV p r o t o n e d g e y e t w e l l  o f 8 MeV. is  defines  since  depends on t h e  chosen.  p r o t o n e d g e , an a n g l e o f 50° was c h o s e n kinematically  f o l d s o v e r a t 2 MeV  from t h e  f o r the alpha detector.  This angle  a t r o u g h l y 5 MeV, c l e a r l y  separating  within  state detector  15 i n C h a p t e r  distinguishable  the depletion  d e p t h maximum  spectrum f o r these measurements,  I I I . The " b i a s  l e v e l " and  - 36 -  "energy window" of either only  The of  side of  the He  angle of  The  the  a l p h a s by  4  p e a k and  t a r g e t was the  and  contributions  vertical  highest  above the  a t 70°  background from the w a l l enclosing  was  made as  the  '•He  this  part of  and  material.  knowledge of  the  total  The  energy  the  873.5  ( a = 5^0  proton  l o s s AE keV  mb,  was  of  the  between the  tubing.  optimized  the  Energy Loss  e x p e r i m e n t was  after deterioration.  i f target  with  region  lining  To  solid  reduce  detector-  to give  the  rate.  of determining The  allowing  possible.  detector  Method  before  the  polyethylene  l a r g e as  2.4.1  thickness  on  possible scattering  c o l l i m a t o r edge s c a t t e r i n g , the  T a r g e t T h i c k n e s s M e a s u r e m e n t s By  purpose of  pulses  proton edge-thereby  t o e l i m i n a t e any  2.4  The  to admit only  analyzed.  collimator with  from the  count  set  proton  p o s i t i o n of  alpha  t o be  r e d u c e d by  the  col limator spacing  were set  t a r g e t mount e d g e s .  c o l l i m a t o r was  state detector  The  He  c o n t r i b u t i o n to the  detector  the  the  SCA  p a r t i c l e s concerned  4  the  the Timing  d e t e r i o r a t i o n was the  target  reaction cross  resonance r = 5 keV,  i n the  This  was  1 9  done w i t h  entirely  section  reaction  Ey = 6 MeV).  to measure the  thickness  o f a p r o t o n beam i n t h e  AE  due  to  actual the  in  target connection  experiment.  t a r g e t was  m e a s u r e d by  F ( p , H e ) 0 * w h e r e 0*+  This  purpose  loss of  i s important  target  k  energy  1 6  l o s s can  be  utilizing  0  16  +  readily  y  - 37 -  converted  to target  thickness.  A calcium  f l u o r i d e t a r g e t , 12 keV t h i c k a t t h e r e s o n a n c e e n e r g y  i n t o a copper b a c k i n g ) , The  was  installed  " a f t e r " t h e (C Dt|)n t a r g e t  2  t a r g e t on t h e beam p a t h  in detail  the y-yie1d  measured as a f u n c t i o n o f t h e i n c i d e n t p r o t o n the  873-5 keV r e s o n a n c e d e t e r m i n e d .  c a l i b r a t i o n o f t h e machine energy.  This  "sandwich  t a r g e t " and s t r i k e  i n s e c t i o n 2.4.2. ( a b o v e 2.6 MeV) was  e n e r g y and t h e p o s i t i o n o f  measurement a l s o p r o v i d e s  the  1 9  F  beam a l l o w e d  target.  t h e r e s o n a n c e p e a k was a d i r e c t m e a s u r e o f t h e e n e r g y  by  the proton  l o s s AE s u f f e r e d  beam.  +  yield  great  measurements  i t was c o n c l u d e d  proton  energy  Hence c a l c u l a t i o n s o f t h e t a r g e t  i s s t a t e d a s an " e q u i v a l e n t  2  indicates  I t may be n o t e d  t o the extent  thickness  from the  the target material  to hold  carbon t h i c k n e s s "  i s a l l (C D )n would y i e l d  f o r a l l thickness  so  in  that a s i m i l a r c a l c u l a t i o n 2  i s 11% l e s s than t h e " e q u i v a l e n t  T h i s was f o u n d  i n s e c t i o n 3-3.1), r e -  t h e t a r g e t m a t e r i a l was p r e d o m i n a n t l y c a r b o n a f t e r  y g / c m . ( s e e A p p e n d i x D).  value which  in detail  l o s s w e r e b a s e d on an a l l c a r b o n a t o m t a r g e t m a t e r i a l  the thickness  assuming t h a t  (discussed  losses o f deuterium from t h e t a r g e t m a t e r i a l  H e bombardment.  that  shift  3  2  flected  3  through  ( C D i ) n t a r g e t d e t e r i o r a t i o n a f t e r H e bombardment a s i n d i c a t e d by  the a l p h a  that  t o pass  The m e a s u r e d e n e r g y  of  The  a  The " s a n d w i c h " t a r g e t was t h e n p l a c e d i n  f r o n t o f t h e f l u o r i n e t a r g e t and t h e p r o t o n the  holder.  2  apparatus and e l e c t r o n i c s a r e d e s c r i b e d  Without a (C D4)n  (evaporated  tt  a  carbon t h i c k n e s s "  thickness value.  measurements c a r r i e d o u t .  t h a t t h e a s s u m p t i o n o f an a l l c a r b o n t a r g e t m a t e r i a l  This  introduces  - 38 -  a p o s s i b l e e r r o r o f <11% i n t h e t h i c k n e s s  c a l c u l a t i o n s , with  o f t h e e r r o r d e p e n d i n g on t h e f r a c t i o n o f t a r g e t m a t e r i a l as  the s i z e  still  remaining  (C D( )n. 2  +  A typical (i)  1 9  F  r e s o n a n c e s h i f t m e a s u r e m e n t was p e r f o r m e d a s f o l l o w s :  The s h i f t spot  of the  ( i e a spot  1 9  F  r e s o n a n c e was m e a s u r e d on a "new"  p r e v i o u s l y unexposed t o He) u s i n g a density  (approximately  vent target d e t e r i o r a t i o n .  An " e q u i v a l e n t  was c a l c u l a t e d f r o m t h e r e s o n a n c e Another had  1 9  proton  3  beam o f l o w c u r r e n t  (ii)  target  0.5  yA/cm ) t o p r e 2  carbon  thickness"  shift.  F a n a l y s i s was c a r r i e d o u t a f t e r t h e same t a r g e t  been exposed  t o a H e beam and a s t a b l e ^He y i e l d  had b e e n  3  attained, (typically  0.1  yA o f H e f o r o n e h o u r ) . 3  An  "equivalent  c a r b o n t h i c k n e s s " was c a l c u l a t e d and h e n c e a t h i c k n e s s yg/cm the (iii)  2  could  be c a l c u l a t e d when t h i s  t h i c k n e s s was c o m p a r e d  carbon t h i c k n e s s " l o s s c a l c u l a t e d from  ( i i ) was c o m p a r e d w i t h loss the  initial alpha  C Di  +  That  the "equivalent  (the l a t t e r having  decide 2  loss in with  results of ( i ) .  The " e q u i v a l e n t  by  spot  thickness  yield).  polyethylene  thickness"  been c a l c u l a t e d f r o m a c o m p a r i s o n of.  by w e i g h i n g and t h e f i n a l  Through t h i s  comparison  m o l e c u l e as a w h o l e o r as a predominant i s t o say, i f the "equivalent  d e p e n d s on t h e l o s s o f d e u t e r i u m , C thickness" loss,  (C Di )n 2  +  thickness  i t was p o s s i b l e t o  whether the target d e t e r i o r a t i o n occurred  the " e q u i v a l e n t  ( i ) and  as a l o s s o f t h e  loss of the deuterium.  (C Dt )n t h i c k n e s s " l o s s , 2  f  i s s u b s t a n t i a l l y greater then t h i s  which than  i m p l i e s a g r e a t e r ;loss  - 39 -  of  d e u t e r i u m atoms  than carbon atoms.  l o s s o f d e u t e r i u m atoms as a  This analysis of  44 y g / c m  2.4.2  2  was and  carried  t h a n a l o s s o f t h e C Di,. m o l e c u l e  rather  2  o u t on t h e p o u r e d  132 p g / c m  thick  2  (C DiJn  "sandwich"  2  targets  (C D )n. 2  i +  10 i s a s c h e m a t i c d i a g r a m o f t h e c h a m b e r u s e d Figure  11  The p r o t o n beam a f t e r target  D, s t r i k e s  the f l u o r i n e  the f l u o r i n e  target  The c o p p e r b a c k i n g was  reaction  Electronics 1 9  F(p,a)  1 6  and w i t h  supplied with  integrator.  The c r y s t a l  used.  A and t h e  b a c k i n g E.  in section  part of the Faraday  The Y ~  r a  thickness  and h o l d e r D i n f r o n t  on t h e f l u o r i n e  0 " w e r e d e t e c t e d i n a NaI  ys  t a r g e t was produced  (Tl) s c i n t i l l a t o r  2.4.1.  cage  assembly  fed into  an  i n the mounted  on  a n d t u b e a r e mounted o u t s i d e t h e  face of the c r y s t a l  t o reduce the Y~ray background.  i s c o v e r e d by 2  inch  The p h o t o m u l t i p i i e r  thick was  n e g a t i v e h i g h v o l t a g e and t h e p u l s e s f r o m t h e a n o d e w e r e f e d  into a preamplifier a m p l i f i e r was  the t a r g e t  removed a s r e q u i r e d  collected  current  A l l but the f r o n t  shielding  both  both  assembly  m o u n t e d on t h e c o p p e r  m o u n t e d on t h e f r o n t  a pho.tomul t i p i i e r t u b e F. chamber.  target  out with  The p r o t o n beam c u r r e n t  Eldorado  i n the target  i s a block diagram of the e l e c t r o n i c s  passing through the c o l l i m a t o r  Measurements were c a r r i e d  lead  a  whole.  measurements.  C.  implies  Apparatus  Figure  of  This in turn  constructed  in this  f e d i n t o a C . I . 1410  and  integration  was  f e d i n t o a C . I . 1435 T i m i n g SCA  laboratory.  linear  time constants of 1 us.  The o u t p u t o f t h e p r e -  amplifier with  differentiation  The p u l s e f r o m t h e l i n e a r  S i n g l e Channel  Analyzer.  amplifier  The "base, l i n e "  Photomultipiier  FIGURE  10:  Tube  SCHEMATIC  DIAGRAM  OF  THE  CHAMBER . S E T - U P  USED  IM T A R G E T  THICKNESS  MEASUREMENTS  BY ENERGY  LOSS  - k]  PREAMPLIFIER  -  FARADAY  Na I  CASE  H.V.  L I NEAR AMPLIFlER  CURRENT INTEGRATOR  SINGLE CHANNEL ANALYZER  ON  OFF  TRIGGER  SCALER  FIGURE  ON-OFF  11:  BLOCK DIAGRAM  OF  TARGET T H I C K N E S S  THE  ELECTRONICS  MEASUREMENTS  USED  FOR  BY ENERGY  LOSS  - 42 -  and  " e n e r g y w i n d o w " o f t h e SCA w e r e s e t t o a d m i t p u l s e s  energies 2.6  fall  i n the region  MeV was s e t u s i n g  ground and y e t s t i l l The p u l s e s  admitted  s c a l e r and c u r r e n t  2.6  MeV t o 10 MeV.  a Ra Th s o u r c e collect  current  by t h e SCA w e r e c o u n t e d by an O r t e c  Proton  2.5.1  "Coincidence"  Beam P r o f i l e  tronics.  The  amount o f i n t e -  target.  Measurements  particle"  sections  technique  f o r measurements o f t o t a l  requires "coincidence"  i t was e x p l a i n e d  beam p r o f i l e )  Scaler.  Electronics  reaction cross  In s e c t i o n 1.1,  430  e n e r g y , t h e number o f 6 MeV gamma  the f l u o r i n e  The u s e o f t h e " a s s o c i a t e d proton  back-  i n t e g r a t o r were t r i g g e r e d on and o f f s i m u l t a n e o u s l y .  striking  2.5  point of  a l a r g e f r a c t i o n o f t h e gamma r a y c o u n t s .  p r o d u c e d , w e r e c o u n t e d by t h e s c a l e r f o r a p r e s e t  grated  the  The base l i n e  a n d was c h o s e n t o r e j e c t room  Hence, f o r each s e t t i n g o f t h e p r o t o n rays  whose gamma r a y  how t h e s p r e a d  e l e c t r o n i c s (Ho  o f the proton  beam ( i e  i n f l u e n c e d t h e a n a l y s i s time o f t h e c o i n c i d e n c e  Hence t h e p u r p o s e o f t h i s  the  proton  beam p r o f i l e  the  use o f s e l f - s u p p o r t i n g t a r g e t s  68).  elec-  p a r t o f t h e e x p e r i m e n t was t o m e a s u r e  t o s e e i f an improvement had been e f f e c t e d r a t h e r than s o l i d  D0 2  copper  through  backed  targets.  The m e a s u r e m e n t "coincidence"  o f t h e beam p r o f i l e  e l e c t r o n i c s used  i n the cross  d i a g r a m o f t h e e l e c t r o n i c s used explanation  incorporated  s e c t i o n measurements.  is illustrated  o f t h e e l e c t r o n i c s ( i n c l u d i n g those  m e n t s ) c a n be f o u n d e l s e w h e r e  (Ho 68).  t h e use o f t h e b a s i c  i n Figure f o r cross  A "Fast-Slow"  12.  A block  A detailed  s e c t i o n measure-  coincidence  system  43  PREAMPLIFIER  -  S . J; . D .  NE  PREAMPLIFIER  102  i  H. V .  BIAS  1 r  LINEAR AMPLIFIER  LINEAR AMPLIFIER  TIMING SCA  T IM I NG SCA  FAST ANTICO IN.  BIASED IAMPL I F I ER  FAST  PULSE  COINCIDENC  STRETCHER  GATE  TIMING SCA  DELAY  GENERATOR  I  GATE  DELAY  GENERATOR  SLOW COINCIDENCE  K I C KSORTER  FAST SLOW  AC SCALER  SCA SCALER  FIGURE  12:  BLOCK DIAGRAM PROTON  BEAM  OF T H E  PROFILE  C SCALER  ELECTRON ICS MEASUREMENTS  USED  IN  THE  - 44  was  employed.  and  anticoincidence respectively.  respective Analyzers  In t h i s  d i s c u s s i o n C and  linear amplifiers to o b t a i n f a s t  coincidences are  -  are  AC Hie  The fed  a m p l i f i e r output  linear  408  B i a s e d A m p l i f i e r f o l l o w e d by an O r t e c  put  of the p u l s e  This  the spread  o f the alpha  timing  SCA  i s set with a  peak.  The  window p o s i t i o n  the c o i n c i d e n c e detector 100 of  keV  the  s t r e t c h e r i s fed  Analyzer.  and  proton  3  He  keV  i n t h e ON  window c e n t e r e d  on  the a s s o c i a t e d p r o t o n s .  signals after  signal  energy  i s a l s o fed  411  Pulse  the 0 to  10 V  the alpha That  OFF  the  a Timing  SCA  dence" channel. (i)  The  In t h i s  output  of  channel  gate  the output  in the s p e c i f i e d  the p u l s e  selection,  two  restricts  SCA  processes  thus  of the  energy  into  The  collimation" range  The  output  of  a "Slow  of Coinci-  In t h i s due  times  r e q u i r e d t o be  t h a t had  range.  longer r e s o l v i n g  alpha-  occur:  SCA  r a t e s w e r e much l o w e r  The  the p o s s i b l e range  S c a l e r ) and  t h e " F a s t C o i n c i d e n c e " g a t e was  coincidence with pulses  (labelled  SCA  state  s e l e c t i o n of a given  hence e n e r g i e s ) of the a s s o c i a t e d p r o t o n s . into a Scaler  the  "Kinematical  of angles  i s a l s o fed  on  the s o l i d  at a g i v e n angle  t h e SCA  out-  l o g i c output  alpha energies (and  The  c o i n c i d e n c e modes.  peak p r o v i d e s  kinematica11y  Ortec  pulse s t r e t c h e r permit  observing  i s to say,  i n t o an  i n p u t r a n g e o f t h e SCA.  feeding  c o i n c i d e n c e and  anti-  selection.  Stretcher.  e n e r g y "window" c e n t e r e d by  their  S i n g l e Channel  i n t o a k i c k s o r t e r and  i s checked  coincidence  " F a s t " c o i n c i d e n c e s and  i n p u t o f t h e k i c k s o r t e r and  spectrum  SCA  b i a s e d a m p l i f i e r and  peak o v e r 100  t o mean  for a l l pulses without  The  S i n g l e Channel  of  taken  into Timing  timing pulses.  then o b t a i n e d  are  s e l e c t e d the second  t o the f i r s t  and  in alpha  coincidence "fast"  less precise timing  are  - k5  permissab1e. fed (ii)  The o u t p u t  -  o f t h i s " S l o w C o i n c i d e n c e " g a t e was  i n t o a S c a l e r l a b e l l e d "C S c a l e r " ,  The o u t p u t  o f t h e " F a s t A n t i c o i n c i d e n c e " g a t e was a l s o r e q u i r e d  t o be i n c o i n c i d e n c e w i t h  t h e SCA o u t p u t  of t h i s "Slow C o i n c i d e n c e " gate  as above.  The o u t p u t  i s fed into a Scaler  labelled  "AC S c a l e r " . Consequently a)  there are three scalers  The "SCA S c a l e r " w h i c h  monitored:  gives the total  number o f a l p h a  particles  d e t e c t e d a t t h e d e s i r e d d i r e c t i o n and o f t h e s e l e c t e d 100 keV energy b)  range.  The "C S c a l e r " w h i c h detected with  gives the total  the selected d i r e c t i o n  number o f a l p h a  particles  and e n e r g y t h a t a r e c o i n c i d e n t  with a proton. c)  T h e "AC S c a l e r " w h i c h  gives the total  detected with the s e l e c t e d d i r e c t i o n  number o f a l p h a  particles  a n d e n e r g y t h a t do n o t h a v e  a coincident proton.  The of  q u a n t i t y m e a s u r e d by t h e "SCA S c a l e r " s h o u l d v e r y n e a r l y e q u a l t h e o t h e r two s c a l e r  2.5.2  Other  Figure ments.  13  Apparatus  quantities.  and Method  i s a schematic  As m e n t i o n e d  diagram  o f t h e chamber s e t - u p  i n s e c t i o n 1.1  and e l s e w h e r e  used  (Ho 68),  p r o t o n d e t e c t o r s were p l a c e d a t kinematica11y c o r r e s p o n d i n g and  63.5°  directions  t h e sum  respectively  (relative  t h e a l p h a s and p r o t o n s  to the incident  3  i n these  t h e a l p h a and angles of  He d i r e c t i o n ) .  had e n e r g i e s o f 3.3  measure-  a n d 15-7  96.2°  For these MeV  respectively.  3  He  '  BEAM =.----A  To Current Integrator  J_  ZL .e-  A B D  =  Collimators  Assembly  = =  Solid  Detector  State  Target  on Water  Assembly  Cooled  Target  G =  NE 102 Plastic Scintillation and Photomu1tip1ier Tube  H  Movable C o l l i m a t o r P Beam P r o f i1e  =  Device  for  Holder  nsulators  Crystal Measuring  +  J  =  Faraday  96 2  Cage  NOTE  FIGURE  13:  SCHEMATIC  DIAGRAM  IN T H E PROTON  OF T H E CHAMBER  BEAM P R O F I L E  SET-UP  MEASUREMENTS  USED  3 - ^  30'  \y63.5'  \  - kl -  The  choice  o f the  target material within  the  sandwich  target  through which the  target.  T h e use  (D) a n g l e alpha  Therefore the  o f kinematical  the  a x i s o f the  minimum t a r g e t  NE102 p l a s t i c  tube were f i x e d a t 63-5°,  angle o f emission.  material  thicknesses  located  a t the  the  scintillator  solid  as p o s s i b l e i n  i n the  used  kinematically correct  locating  todefine the  a small  crystal  state detector  i n c h d i a m e t e r ) c o l l i m a t o r mounted o n t h e was  energy  alpha  particle  He beam d i r e c t i o n s .  Since  and  target  good  a small  An a n g l e o f 30° was c h o s e n a s a com-  d i r e c t i o n o f t h e ^He p a r t i c l e s .  and  t h e .tyabeam w i t h  s c a t t e r i n g e f f e c t s on i t s o r i g i n a l  desired  amount o f  collimation toobtain  i t i s d e s i r a b l e t o have as l i t t l e  promise between the  the  p a r t i c l e s must p a s s when p r o d u c e d  a n g u l a r d i v e r g e n c e depends on d e t e c t i n g r e s o l u t i o n and small  influences  a s s e m b l y was m o v a b l e  a n g l e o f 96.2°. front centre  range o f p r o t o n e n e r g i e s  c o r r e c t p o s i t i o n o f the  and p h o t o m u l t i p i i e r  solid  A small  o f the  (0.125  proton  detector  a n d was e m p l o y e d i n  state detector.  The a l p h a  detector  p o s i t i o n was f o u n d a s f o l l o w s : ( i ) The alpha of  detector  was l o c a t e d  3  tostrike  dence e l e c t r o n i c s as d e s c r i b e d Scalers  were m o n i t o r e d .  the  per  i n the  region  and u s i n g  2.5-1, t h e  The s c a l e r s were a l l o w e d  number o f c o u n t s t o g i v e  scaler  target  insection  sufficient  angle  assembly angle,  with  o f 1° t 0.2°.  coinci-  SCA, AC a n d C  statistical  error  of interest,  respect For  the  t o count f o r a  a maximum 3-5%  T h e r a t i o AC/C was m e a s u r e d a s a f u n c t i o n o f t h e  steps  correct  ts°.  96°  ( i i ) T h e H e beam was a l l o w e d  (iii)  a t a p p r o x i m a t e l y the  t o the  alpha  detector  i n c i d e n t beam d i r e c t i o n , , i n -  e a c h a n g u l a r p o s i t i o n , t h e 1 0 0 keV w i n d o w  -  of  the alpha  The  channel  minimum AC/C  hS  Timing  -  SCA  was  r a t i o corresponds  coincidence to anticoincidence matically  best  stps of 0.5°  -  centered  on  the alpha  to the h i g h e s t counts was  of  i n d i c a t e s the  position.  The  0.2°  about the d e t e c t o r assembly a n g l e  taken  process  which  ratio  peak.  repeated  with  kine-  angular found  above.  After  setting  located The of  in the plane  same p r o c e s s  Timing  of minimizing  pulses  plastic  the " z e r o SCA.  "proton"  scintialltor I t was  t h e a l p h a d e t e c t o r must  i n c i d e n t He  beam and  3  t h e AC/C  r a t i o was  the v e r t i c a l  occurred  necessary  and  carried  position  alpha  at different  be  the  proton  out  as a f u n c t i o n  relative  to the  detector.  plane  in the s o l i d times  pulses occurred  The  the p l a s t i c  necessary  decay time o f  points.  time  a m p l i f i e r ) was  to delay  d e l a y on  varied.  d e l a y and  a d e l a y was  t h e AC/C  ratio.  The  than  the proton  the Timing AC/C  to the  unequal  SCA  r a t i o was  chosen t o correspond  c h e c k more a c c u r a t e l y t h e a n g u l a r  of  a t t h e same t i m e , s i n c e i t  t r i g g e r e d the  fast  due  state detector  to ensure t h a t the " z e r o c r o s s o v e r " p o i n t s  timing pulse occuring e a r l i e r  The  detected  crossover" point which  Hence i t was  To  the  from " c o i n c i d e n t " events  " c o i n c i d e n t " proton  Timing  (ie  position,  above).  pulse shapes.  is  d e f i n e d by  the d e t e c t o r " h e i g h t "  def ined  and  the c o r r e c t angular  l o g i c out  put  scintillator  the corresponding pulse  t o match the  (following  pulse of  resulted  in a  "alpha"  one.  "zero-crossover"  the proton  channel  m e a s u r e d as a f u n c t i o n o f t h e to the c e n t r e of the  p o s i t i o n of  the alpha  the  flat  linear time  valley  d e t e c t o r , i t was  on  - 49 -  necessary  t o a s c e r t a i n w h e t h e r t h e minimum  100 keV across  window b e i n g the peak.  readjusted centered as  until  t h e AC/C  on t h e a l p h a  the alpha  on t h e a l p h a  The a n g u l a r  t h e c o r r e c t one  After  centered  r a t i o corresponded  to the  p e a k a s t h e w i n d o w was  p o s i t i o n of the alpha  r a t i o minimum  peak.  AC/C  swept  d e t e c t o r assembly  corresponded  t o t h e 100 keV  T h i s angle o f the alpha  d e t e c t o r was  was  window  accepted  kinematically.  d e t e c t o r was  located  and t h e r i g h t t i m e d e l a y  determined,  a m o v a b l e c o l l i m a t o r d e v i c e c o n s i s t i n g o f two o v e r l a p p i n g p l a t e s , a s  shown  in F i g u r e  to  14, was  installed  measure the p r o t o n were 0.125"  beam p r o f i l e s .  i n diameter  the s e l f - s u p p o r t i n g locking  section  sliding  plate  situated then  over  taken  on t h e f r o n t o f t h e p l a s t i c The c i r c u l a r  2  B of plate  I over  plate  the v e r t i c a l  I until  slot  II was  The v e r t i c a l  one o f t h e h o l e s o f s e c t i o n  of section  B.  vertical  moved t o t h e l e f t .  Coincidence  detector  in the v e r t i c a l  -7.35°.  The  ratio  l  v  = C/(C + AC)  were taken relative alized  direction.  This yielded  These angular  i n t e n s i t y v a l u e was  and  then  C was  measurements were  collimator positions  f o r each o f the c o l l i m a t o r p o s i t i o n s about t h e c e n t r e  relative  C and D  p r o f i l e was m e a s u r e d by  the c e n t r e o f the s c i n t i l l a t o r  f o r each o f the succeeding  4 and 5 as p l a t e  in sections  and s u b t e n d e d an a n g l e o f 3-70° a t t h e c e n t r e o f  (C Di4)n target.  II o v e r  holes  scintillator  1, 2, 3»  an i n t e n s i t y v a l u e  l i n e of the proton  p o s i t i o n s w e r e 0 ° , t 3.69°,  determined  by c a l c u l a t i n g t h e  f o r e a c h c o l l i m a t o r p o s i t i o n w h e r e t h e C and AC  from t h e i r r e s p e c t i v e  scalers after several  i n t e n s i t i e s were n o r m a l i z e d  i n t e n s i t y as a f u n c t i o n  values  thousand counts.  The  t o a peak i n t e n s i t y o f 1 and t h e norm-  of the v e r t i c a l  angular  positions  i s presented  - 50 -  ,11  -  Movable  Plates  Open S e c t i o n -  in  Open V e r t i c a l  - 5 Open - 1  Holes  Open H o l e  FIGURE  Plate  Slot (Diam =  0.125")  (Diam =  0.125")  14:  DIAGRAM OF COLLIMATOR DEVICE FOR MEASURING HORIZONTAL AND VERTICAL PROTON BEAM PROFILES  - 51 -  i n s e c t i o n 3-^-3-  The h o r i z o n t a l over plate  p r o f i l e was m e a s u r e d b y f i r s t  locking  the centre of the p l a s t i c s c i n t i l l a t o r . t h e 0.125° d i a m e t e r  I until  extreme  r i g h t o f t h e open s e c t i o n  Plate  hole of section A.  Plate  section  A of plate I  II was t h e n s l i d  D was  located  on the  I I was t h e n moved t o t h e l e f t  in small s t e p s .  C o i n c i d e n c e measurements were taken f o r h o r i z o n t a l  positions  the c e n t r e l i n e ) o f  (about  18.179° a n d - 9 - 9 5 8 ° . intensities a function  section  over  angular  0 ° , ± 0.921°, t 2 . 7 6 2 ° , - 4 . 5 7 9 ° , +6.396°  As i n t h e c a s e o f t h e v e r t i c a l  profile,  the r e l a t i v e  1^ = C/(C + AC) w e r e n o r m a l i z e d t o a p e a k o f 1 a n d p l o t t e d a s of the h o r i z o n t a l  3.4.2.  angular p o s i t i o n .  The r e s u l t s a r e p r e s e n t e d i n  -  52  -  CHAPTER  II I  EXPERIMENTAL OBSERVATIONS AND CALCULATIONS  3.1  General  Introduction  This chapter  presents  the experimental  preparation  techniques  observations concerning  of the self-supporting  (C D^)n  "sandwich"  2  t h e i r p e r f o r m a n c e when s u b j e c t e d t o t h e H e beam o f 6 9 0 k e V . 3  i s a s c e r t a i n e d by a l p h a y i e l d 2  H ( H e , p ) H e ) , as w e l l 3  4  technique extended  ( i e the  1 9  F  in this  and  proton  horizontal  those obtained  3.2  resonance  i n the "sandwich"  also presented  poured  without and  the presence milky  4  The r e s u l t s o f t h i s  loss was layer  study a r e  compared  b a c k e d t a r g e t s (Ho 6 8 ) .  Preparation 2  o f carbon  f i l m s were f i r s t  4  layers.  The p o u r e d  i n colour w h i l e the evaporated As e x p l a i n e d to determine  in section  t e s t e d on c l e a r  extremely  2.2.2,  of the  testing  the average polyethylene t h i c k n e s s  +  showed a maximum o f 1 5 % v a r i a t i o n This appeared  uniform  f i l m s appeared  t  ( C D i ) n p e r ml o f X y l e n e , 2  slides  f i l m s appeared very  2  f o r the s l i d e .  extended  and t h e p r o f i l e s  as a f u n c t i o n o f t h e c o n c e n t r a t i o n o f (C Di )n  a given s l i d e  the reaction  t h e measurements o f t h e v e r t i c a l  are presented  copper  (C D )n  t h e c o n c e n t r a t i o n o f 1 . 3 6 mg  thickness  D20  forsolid  f i l m a l o n e was u s e d  for a slide  from  The t a r g e t p e r f o r m a n c e s t u d y  Fianlly  beam p r o f i l e s  u n i f o r m and t r a n s p a r e n t . 2  Performance  measurements as a f u n c t i o n o f t h e carbon  chapter.  and e v a p o r a t e d  slightly  (C D )n  shift).  target.  S e l f - S u p p o r t i n g Target  Both  (of the alphas  t a r g e t s and  a s t a r g e t t h i c k n e s s m e a s u r e m e n t s by t h e e n e r g y  to include alpha y i e l d  thickness  with  measurements  the different  from  i n Xylene.  t h e poured  Using  samples o f  the average polyethylene  t o be due t o t h e manner  i n which the  - 53 -  hot s o l u t i o n  spread  In  the average  addition,  variation sweeping  itself  from s l i d e motion  11 y g / c m ) . 2  ment  o f w h i c h was  difficult. maximum  p r o b a b l y due t o t h e s p e e d o f t h e hand  across the s l i d e . 2  control  p o l y e t h y l e n e f i l m t h i c k n e s s showed a 10%  to slide,  t h i c k n e s s o f 44 y g / c m i  across the s l i d e ,  Hence t h e o b s e r v e d a v e r a g e p o l y e t h y l e n e  i s s u b j e c t t o a p o s s i b l e v a r i a t i o n o f t 25%  (ie  T h i s u n c e r t a i n t y e s t i m a t e i n c l u d e s w e i g h i n g and a r e a measure-  errors.  An  e x a m p l e o f t h e r e ' a t i v e u n i f o r m i t y o f t h e p o u r i n g p r o c e s s was o b s e r v e d  in  t h e t h i c k e r poured  polyethylene films.  ( C D ) n p e r ml o f X y l e n e 2  H  yielded - 25%  t a r g e t samples  Due t o t h e c a l i b r a t i o n section  2.2.1),  ( i e three times the c o n c e n t r a t i o n mentioned  o f an average  ( i e 3 x 44 y g / c m  2  H e r e a c o n c e n t r a t i o n o f 4.08  (C^D^n t h i c k n e s s e q u a l  t o 132  mg above)  yg/cm  2  thick).  and m o n i t o r e r r o r s o f t h e e v a p o r a t i o n p r o c e s s ( s e e  the evaporated  (C Dt )n f i l m s o f 135 y g / c m 2  2  +  were s u b j e c t t o  an u n c e r t a i n t y o f t 12 y g / c m . 2  The  carbon  thick  layer  thicknesses o f the "sandwich"  (C Di )n, were each 2  t  2  2  [|  contributed  weighing o f a carbon in  F i g u r e 5).  for  the carbon 2  lt  yg/cm  included  thickness error t h e (C Di )n 2  t  2  error,  v a r i a t i o n across the s l i d e .  The  since the  layer  layers evaporated over the basic  layer v a r i a t i o n  (C D )n " s a n d w i c h "  +  t o the carbon  layer section  A l l carbon  f o r t h e 44  s u b j e c t t o an t 17% e r r o r due t o w e i g h i n g  c a r b o n t h i c k n e s s v a r i a t i o n and (C Di )n (C D )n v a r i a t i o n  targets,  (as i l l u s t r a t e d  target  s t u d y a n d e v a p o r a t e d f o r t h e 135  sandwich  yg/cm , t h i c k  t a r g e t s , w e r e m e a s u r e d by t h e t h i c k n e s s m o n i t o r .  2  Hence  5k  -  they were s u b j e c t monitor errors for  to a smaller  as e x p l a i n e d  errors  c o m p o s e d o f t h e c a l i b r a t i o n and  in section  the evaporation of a s i n g l e  possible  2.2.2.  10 p g / c m  2  T h i s amounted t o  carbon  in the estimates of the various  "sandwich" t a r g e t s  i s shown  TABLE  (C Dt )n T h i c k n e s s 2  error  -  i n Table  1:  2  layer  10%  A summary o f t h e  thicknesses  f o r the  1.  L a y e r T h i c k n e s s e s and t h e i r Errors f o r the "Sandwich" Targets  (C Di )n  t  layer.  t  +  layer error  Single carbon layer (10 y g / c m t h i c k ) e r r o r 2  kk y g / c m (poured) 132 y g / c m (poured)  +  2  2  135 y g / c m (evaporated) 2  Compared w i t h an  the weighing  +  15%  of  the thickness  + 10% (T mon i t o r )  + 8.3%  + 10% (T m o n i t o r )  t e c h n i q u e , use o f t h e t h i c k n e s s  thickness in  o f t h e poured  (C D )n 2  L f  samples.  w o u l d be r e d u c e d  section  2.2.1),  layer  thereby  thickness  areas  (e.g.  n  The e r r o r  n  f o r poured  as w e l l  monitor  permitted  as y i e l d i n g  a more a c c u r a t e  a  estimate  l a y e r was o b t a i n e d a f t e r w e i g h i n g t h e i n t h e measurement o f t h e c a r b o n  through b e t t e r reducing  thickness  In a d d i t i o n  (C2 u)  to monitor the carbon e v a p o r a t i o n large  layer  f o r the thickness.  "sandwich" target  (weighed)  + 14%  immediate e s t i m a t e o f t h e carbon  lower u n c e r t a i n t y  17%  e v a p o r a t i o n "geometry"  the error targets.  (as m e n t i o n e d  i n t h e measurement o f t h e By u s i n g  the "thickness  t o t h e o r d e r o f t k%,  2 cm x 2 cm) o f t a r g e t  layer  followed  monitor"  by w e i g h i n g  sandwich samples, the e r r o r  i n the  - 55 -  t h i c k n e s s o f t h e (C D )n 2  The  carbon  l a y e r s appeared  the "sandwich"  structure,  minimum p o s s i b l e h e a t appear  The  l a y e r c o u l d be r e d u c e d  tt  v e r y u n i f o r m i n c o l o u r and t e x t u r e . the carbon  radiation  t o damage t h e e x p o s e d  poured  (C Dt )n t a r g e t 2  10% s u c c e s s  water  rate of stripping  surface.  This  The l a r g e f a i l u r e  decreased  by s t r i p p i n g  than  did not  w e r e m e c h a n i c a l l y much s t r o n g e r t h a n The e v a p o r a t e d  t h a n t h e 75%  success  rate with the evaporated  t a r g e t s had o n l y  r a t e f o r t h e poured  t a r g e t may h a v e b e e n  a n d p i c k i n g - u p i n a medium o f l o w e r s u r f a c e t e n s i o n  water.  i s $155-00 p e r g (De  c u r r e n t market p r i c e o f (C D )n  The  2.2.1),  from t h e g l a s s s l i d e s and p i c k - u p from t h e  i s much l e s s  targets.  complete  p o l y e t h y l e n e f i l m on t h e s l i d e .  t h e e v a p o r a t e d o n e s o f t h e same t h i c k n e s s . a  To  evaporation, carried out with the  (as d e s c r i b e d i n s e c t i o n  sandwiches  t  t o t h e o r d e r o f t 8%.  2  the success  tf  69).  Considering  r a t e s , amount o f ( C D i ) n r e q u i r e d e t c . , t h e p r i c e p e r u s a b l e 2  t a r g e t s a m p l e [ f o r 44 y g / c m  2  thick  t  (C D )n] 2  was 7 c e n t s f o r t h e p o u r e d  )+  ( C D ) n p r o c e s s w i t h o u t u s i n g t h e T m o n i t o r a n d 41 c e n t s f o r t h e e v a p o r a t e d 2  t+  polyethylene process.  Using the T monitor  many u s a b l e t a r g e t s w o u l d less e x t e n s i v e weighings would  Two  be r e d u c e d  slides  the s l i d e  needed f o r t h i c k n e s s e s t i m a t e s . cents per usable target  t o observe  "cross-1inking"  e v p o r a t i o n , 3 times as  be a v a i l a b l e f r o m t h e p o u r i n g p r o c e s s due t o t h e  holding evaporated  gamma r a d i a t i o n through  t o 2.3  f o r carbon  ( C ^ i ^ n sandwich  Hence, t h e p r i c e  sample.  t a r g e t s were s u b j e c t e d t o  the p o s s i b i l i t y o f improving the target s t r e n g t h  (see s e c t i o n  2.2.4).  The t a r g e t  s u b j e c t e d t o 3 M e g a r a d s showed no v i s i b l e  samples taken  improvement  from  in their  - 56 -  mechanical stripping could  strength  and e x p e r i e n c e d t h e same l o w 10%  and p i c k - u p .  n o t be s t r i p p e d  interaction  i n which  The " s a n d w i c h " t a r g e t  by no means c o n c l u s i v e , d i d i n d i c a t e improved glass  through "cross-1inking".  This implied a type o f  onto the substrate.  that the target  films  Such s t r i p p i n g pounds  from the g l a s s  Evaporating a stripping  agents might  slides  after  This  s t r e n g t h might agent  s l i d e before target preparation could a i d i n stripping  "hardened"  during  f i l m s u b j e c t e d t o 12 M e g a r a d s  from the g l a s s s u b s t r a t e . t h e f i l m was h a r d e n e d  success rate  extensive  test, be  onto t h e ;  o f f such  radiation  exposure.  be Na C I , d e t e r g e n t s o r s o l u b l e o r g a n i c com-  (Ko 66).  3.3  T a r g e t Performance Under t h e He  3.3-1  A l p h a Y i e l d and Energy  3  Beam  L o s s T h i c k n e s s f o r R e g u l a r Runs  A typical  s o l i d s t a t e d e t e c t o r spectrum f o r t h e a l p h a y i e l d measurements i s  presented  in Figure  in  For  section  The c h a r a c t e r i s t i c s  symbol  target  (I, I I ,III or IV ) indicates Q  s a m p l e was t a k e n .  The second  symbol  fourth optional  symbol  R indicates  samples.  target that  3  It includes  the " f i n a l  slide  (A, B, C e t c ) i n d i c a t e s  r e l a t i v e t o t h e H e beam d i r e c t i o n  T a b l e 2 i s a summary o f t h e t e s t i n g  the p a r t i c u l a r  The t h i r d symbol  d e f i n e s o n e o f t h e beam s p o t s on t h i s  position  discussed  i s i d e n t i f i e d by 3 o r k s y m b o l s .  t a r g e t sample from t h e g i v e n s l i d e .  The  o f the spectrum were  2.3-2.  convenience a p a r t i c u l a r  first the  15-  carried  sample,  [S(l),  from  The which  the p a r t i c u l a r  S(2), o r  S(3)]  up t o 3 s p o t s p e r s a m p l e .  t h e t a r g e t has been r e v e r s e d i n after  its first  testing.  o u t on t h e b a s i c " s a n d w i c h "  alpha y i e l d "  (ie after  300  y c o f H e on 3  target target)  57  i  I O O K P  r  r  i  MeV P r o t o n s  16.7  5  MeV  4  He  IOK  IK  z z < X  o  \ cn  £  1 0 0  •; P r o t o n  Edge  O  o  10  48  96 C H A N N E L  FIGURE  15=  A TYPICAL  SOLID  STATE  DETECTOR  144  192  240  N U M B E R S P E C T R U M FOR T H E A L P H A  YIELD  MEASUREMENTS  TABLE 2:  TARGET  (C Di+)n THICKNESS (yg/cm ) 2  2  BACK C FRONT C LAYER LAYER THICKNESS THICKNESS (yg/cm ) (yg/cm ) 2  2  A SUMMARY OF THE ALPHA Y I E L D AND ENERGY LOSS THICKNESS TESTING CARRIED OUT ON THE BASIC "SANDWICH" TARGET SAMPLES  "EQUIVALENT CARBON THICKNESS" BY F A N A L Y S I S ( y g / c m ) AT t = 0 m i n , t AFTER TARGET RECEIVED H e E 60 y c , E 300 y c 1  9  2  3  " F I N A L ALPHA Y I E L D " (COUNTS/yC) AFTER 60 yC 300 yC  "EQUIVALENT H e BEAM POLYETHYLENE CURRENT THICKNESS" (pA) (yg/cm ) 3  2  1 AS (1 )  40.0i6.0  10.oil.7  8.Oil.4  42.0+12.0  1300i36  7.83 0.22  0.05  1BS ( I )  40.0+6.0  10.0^1.7  8.oil.4  41.2+12.0  1780+42  10.7^0.25  0.015  IBS(2)  40.0i6.0  10.0±1.7  8.0+1 .4  60.0il2.0  453±21  2.73*0.13  0.09  IBS (3)  40.0±6.0  10.0±1.7  8.Oil.4  63.2±12.0  420i20  2.53+0.12  0.24  1 IAS (1)  38.0+5.8  10.Oil.7  8.0±1.4  189±13  1.15i0.08  0.15  1 IBS(l)  38.0+5.8  10.Oil.7  8.oil.4  217+15  1.31+0.09  0.12  1 ICS(l)  4o.0±6.0  10.0±1.7  8.Oil.4  21iii4  1.27i0.08  0. 14  1 1 I A S ( 1 ) 125.0±17.5  io.oti.o  11.0+1.1  ioooi32  6.02+0.19  0.08  136.0*12.1  11.0+1.1  12.0±1.2  1050+32  6.32i0.20  0.10  1110+33  6.69i0.20  0.08  I V  o  1 1 ICS(1) 125.0+17.5  io.oil.o 1 1 . o i l . !  132.0+12.0  37.2il2.0  ioo.oii2.o  +  Note:  t = time  - 59 -  measurements and t h e " e q u i v a l e n t 19  carbon t h i c k n e s s " determinations  by t h e  F  resonance s h i f t  ( s e e s e c t i o n 2.k).  method  Two s a m p l e s w e r e  tested  up t o 6 0 y c o f H e a s a p r e l i m i n a r y t e s t o f t h e a l p h a  errors  quoted  yield.  3  i n a l l the alpha  number o f c o u n t s . determined  The " e q u i v a l e n t  from the r e l a t i v e  quantities.  The e r r o r s  the estimates  are the s t a t i s t i c a l  polyethylene  errors  introduced  i n the "equivalent  on a p o s s i b l e r e s o n a n c e s h i f t contains  yields  of the various  errors  by t h e a l p h a  targets  3  H e beam c u r r e n t s  carbon  composite  are listed.  (on a c i r c u l a r  Targets  from s l i d e s  polyethylene  films.  polyethylene  f i l m and had been s u b j e c t e d  before  3  H e beam  t h i c k n e s s e s " a r e based 3 keV. The t a b l e a l s o  layer thicknesses  beam s p o t  A)  Final  The t a r g e t from s l i d e  as  The  o f 0 . 1 6 0 cm) f o r a l l  IV contains Q  poured  an e v a p o r a t e d  t o 3 M e g a r a d s o f gamma r a d i a t i o n  bombardment.  deuterium content  hk y g / c m  and t o t a l  2  t h i c k poured  thickness  IAS ( 1 ) and I B S ( l ) w e r e c o m p a r e d a f t e r  60 y c o f H e . 3  "equivalent ly.  layer.  may be s u m m a r i z e d a s f o l l o w s :  Targets with  for the  I , II a n d I I I a l l c o n t a i n  T h e t e s t i n g o f t h e t a r g e t s composed o f a p p o x i m a t e l y polyethylene  i n the  yield  " s a n d w i c h " t a r g e t s a m p l e s as w e l l as t h e u n c e r t a i n t i e s i n each incident  The  thickness" errors are  error of -  measurement  only  The a l p h a  yields  they  had d e c r e a s e d  such t h a t t h e  (r. Di )n t h i c k n e s s e s " w e r e 7.83 a n d 10.7 y g / c m 2  +  The s u b s t a n t i a l l y compared w i t h  lower  "equivalent  the "equivalent  carbon  polyethylene thicknesses"  l o s s o f d e u t e r i u m atoms t h a n c a r b o n atoms w h i c h predominant  had b e e n bombarded  2  respective-  thicknesses" implies a greater  i n turn  implies a  l o s s o f d e u t e r i u m atoms r a t h e r t h a n a l o s s o f t h e G2D14  - 60 -  molecule  as a w h o l e .  The a l p h a y i e l d  t o o u n s t a b l e t o make a c o m p a r i s o n  d e t e r i o r a t i o n was  still  of the targets f o r thickness  uni f o r m i t y . Target u n i f o r m i t y Comparison o f the alpha y i e l d as  illustrated  curves  f o r t a r g e t s IBS (2) a n d IBS(3),  i n F i g u r e 16, s e r v e d a s a c o m p a r i s o n  between  dif-  f e r e n t beam s p o t s on t h e same t a r g e t s a m p l e .  The p l o t t e d  curves  y-axis yc settings  for  are separated  which  parallel agree  each a l p h a  to within  identical  are normalized  yield  F  (see Table  uncertainties.  t h e 0.25"  2).  self-supporting  are: a rapid  t o 100  yc w i t h the curve  Hence when  The t a r g e t s a m p l e s  as a f u n c t i o n o f t h e t o t a l  o f the curves 60  yc) i n counts/yc  reflecting  a slow  integrated  region.  decrease  yc; stabilizing  r e g i o n and  i n the alpha  of the d e t e r i o r a t i o n  subsequent decrease i n  yield.  " e q u i v a l e n t C t h i c k n e s s " f o r t a r g e t IBS (2) as c a l c u l a t e d a n a l y s i s was 60.0  with After 37.2  ( a t 300  are roughly  t o t h e same y c v a l u e , t h e c u r v e s a r e  uniform across  the f i r s t  the alpha  The  The c u r v e s  on t h e t a r g e t i s c o n s i s t e n t a c r o s s t h i s  over  150  error  the experimental  Characteristics  1 9  alpha y i e l d s "  target deterioration  charge  was m o n i t o r e d .  the s t a t i s t i c a l  within  then, are very  by  count  and t h e " f i n a l  t h e two c u r v e s  the  because o f the d i f f e r e n t  yield  the estimated 300  t 12.0  total  yg/cm  t 12.0  yg/cm . 2  This  a t time  t h i c k n e s s o f 58.0  y c o f H e on t a r g e t , 3  2  by t h e  t = 0 min. c o n s i s t e n t t 9-1  yg/cm  2  by w e i g h i n g .  t h e " e q u i v a l e n t C t h i c k n e s s " was  is substantially  g r e a t e r than  the "equivalent  10*87&^  1  i  r  i  9-  1  (1)  =  Target  I B S ( 3 ) , Q = 4.5 y C  (2)  =  Target  I B S ( 2 ) , Q. = 1.5 uC  5-  O  m -  Q Z <  5-1 * 44  2-^  O O  O  A  ess  I  I  I  (I)  I I  1  oo  I  I  1  1  I  T 1  I  1  I  I  eo  to |O -| a  ON  ° ° O Ooooo ll i B  O  I  i j  (2)  ,j  1  1  3  1  I I I II  I I i  1  I  3 .5-4 _, U J  4-  V  < I  CL  3-  *-l  JL_L  10'  0 10 2 0  _L 50  100  TOTAL FIGURE  16:  ALPHA  Y I E L D A S A FUNCTION  I B S ( 2 ) AND I B S ( 3 )  150  INTEGRATED BEAM OF T H E T O T A L  300  250  200  CURRENT  INTEGRATED  350  i^C)  BEAM C U R R E N T ON T A R G E T  FOR T H E T A R G E T S  "  - 62 -  (C D )n 2  t h i c k n e s s " o f 2.73  t t  mentioned a  i n A) a p r e d o m i n a n t  yg/cm  agrees with  target  IBS(2) w i t h i n  different roughly  target  parallel  statistical very are  (in section  and t h e " f i n a l  uniform across  istics  apply  in Figure  3-3.2), s e r v e d  This  alpha  the whole s l i d e  as d i s c u s s e d  error.  18,  IIAS(l),  19 a n d 20  as a c o m p a r i s o n  that  between  The c u r v e s a r e  the target  and t h e t a r g e t  sample.  samples a r e  deteriorations  The same c u r v e  character-  inB).  Comparison o f samples from d i f f e r e n t s l i d e s C o m p a r i s o n o f t h e r e s u l t s f r o m C) w i t h comparison between t a r g e t case the y i e l d alpha  thickness  that  polyethylene  (both  appeared  roughly  parallel.  f i l m s from s l i d e  p r o c e s s does n o t y i e l d  as a In t h i s  The  d i f f e r e d by more t h a n t h e s t a t i s t i c a l  the pouring  behaviour of the targets  t h o s e f r o m B) s e r v e d  samples from d i f f e r e n t s l i d e s .  curves s t i l l  y i e l d " values  indicating  The  which  2  y i e l d s " agree w i t h i n the  illustrates  f r o m sample t o  yg/cm  slide  s a m p l e s f r o m t h e same s l i d e .  errors.  consistent  t 12.0  than  C thick-  deteriorations f o r targets  I I B S ( l ) and I I C S ( l ) , as i l l u s t r a t e d respectively  The " e q u i v a l e n t  the possible  C o m p a r i s o n o f s a m p l e s f r o m t h e same yield  i m p l i e s (as  l o s s o f d e u t e r i u m atoms r a t h e r  IBS(3) a t t = 0 m i n was 63.2  Comparison o f the alpha  D)  which  2  l o s s o f t h e C2D4 m o l e c u l e a s a w h o l e .  ness" of target  C)  i 0.13  "final  errors  exactly  t h e same  to slide.  composed o f a p p r o x i m a t e l y  135  yg/cm  2  thick  p o u r e d a n d e v a p o r a t e d ) may be s u m m a r i z e d a s f o l l o w s :  - 63 -  i)  Evaporation  vs  Pouring  Measurement o f t h e a l p h a and  IV  0  served  as a comparison o f the m e r i t s  2  illustrated  in Figure  the  experimental  errors.  that of the " t h i n n e r "  of  the " f i n a l preparation  alpha  behaviour  described  i s very  in B).  and  curves within  s i m i l a r to  Target d e t e r i o r a t i o n  y i e l d s " a p p e a r t o be i n d e p e n d e n t o f t h e m e t h o d "sandwich" target  - w h e t h e r by t h e  pouring  technique,  Effect of " c r o s s - l i n k i n g " Subjecting  the evaporated  (C D )n 2  4  "sandwich" targets  gamma r a d i a t i o n d i d n o t a p p e a r t o m o d i f y or  final  alpha  thickness. greater iii)  The  The two c u r v e s a r e i d e n t i c a l  The t a r g e t  targets  of the  or evaporating  17-  IIIAS(l)  of evaporating  deterioration.  t  are  and  deterioration for targets  (C Dt )n a s r e g a r d s t o t a r g e t  pouring  ii)  yield  yield  as compared w i t h  determined tent with 146.0 t the This  conclusive  d o s e o f r a d i a t i o n may a i d i n i m p r o v i n g  target,  MICS(l),  the t o t a l  14.4 y g / c m  target  estimated  132.0 t  t o 300 y c o f H e , a n o t h e r  alpha  yield  n e s s " o f 6.69 y g / c m . 2  large difference  12.0 y g / c m  "sandwich"  3  2  target  1 9  F  i n these f i n a l  thickness"  is consis-  thickness After  of  subjecting  a n a l y s i s was c a r r i e d o u t .  t o an " e q u i v a l e n t  A g a i n , as w i t h  C  which  C t h i c k n e s s " o f 100.0 t  corresponded  performance,  The " e q u i v a l e n t  (by w e i g h i n g and T m o n i t o r ) .  2  y i e l d e d an " e q u i v a l e n t  The f i n a l  target  and a  thickness  was t e s t e d .  a t t = 0 m i n . was  deterioration  the poured t a r g e t o f s i m i l a r  The t e s t h o w e v e r was by no means  F i n a l d e u t e r i u m c o n t e n t and t o t a l A third  the target  t o 3 Megarads  the thinner  "equivalent  12.0 y g / c m . 2  (C Dt )n t h i c k 2  f  t a r g e t s , the  thicknesses"  implies a  1  ~~I  9 -  81 — 6  O =  Target I V  A =  Target  0  -  S-  I I I AS (1)  4 -  ^  3  O  tn hz §  io . 4  ON  6-  U J  5-  <  X Q.  3 J  \o  o o A  G  AA A1 A  o  °  2-^  io-  ° A  ©  I 1 i  h  I  I  _I_JL  0 10 20  50  100  TOTAL FIGURE  17:  ALPHA YIELD  TARGETS  150  200  INTEGRATED BEAM  A S A FUNCTION  I I IAS(1) AND I V  Q  OF T H E T O T A L  250  CURRENT INTEGRATED  300  350  (^tC) BEAM C U R R E N T ON T A R G E T  FOR T H E  -  predominant  65  -  l o s s o f d e u t e r i u m atoms  C2D4 m o l e c u l e as a w h o l e . deterioration  appears  rather  The p r o c e s s  than a loss o f the  involved  during  target  t o be t h e same a s i n t h e c a s e o f t h e t h i n n e r  targets. iv)  A comparison  300 y c o f H e on a g i v e n  After  3  (C Di )n 2  o f " t h i n " and " t h i c k " t a r g e t s  +  thickness"  ( w h i c h d e p e n d s on t h e c o n c e n t r a t i o n  atoms) t o t h e " e q u i v a l e n t concentration  o f carbon  7.34  x IO  This - 2  t  2  f o r target  culated  (using  IBS (2)  ("thin" target)  thickness" values, the  the formulae developed then gives  i n Appendices  ratio f o r target  that  terium  t o carbon  3.3.2 Alpha Y i e l d  I I I C S ( l ) was 0 . 1 0 0 - 0 . 0 1 5 .  the experimental  the " f i n a l "  i n the target  The  of the material.  I B S ( 2 ) was 0 . 1 1 0 - 0 . 0 3 9 d e u t e r i u m atoms p e r  c a r b o n atom and f o r t a r g e t ment, w i t h i n  cal-  B and C ) .  the concentration  number o f d e u t e r i u m atoms p e r c a r b o n a t o m This  was  f o r b o t h d e u t e r i u m a n d c a r b o n may. be  r a t i o o f t h e s e two numbers  target,  I I ICS (1) ( " t h i c k " . t a r g e t )  From t h e " e q u i v a l e n t 2  in the total  These r a t i o s agree w i t h i n the  2  number o f atoms p e r c m  ( w h i c h d e p e n d s on t h e  concentration  and f o r t a r g e t  - 2  1.00 x 1 0 " .  error.  thickness"  t o carbon  2.1 x I O  t  was 6 . 6 9 x 1 0 ~ experimental  ratio  carbon  of deuterium  atoms) i s an i n d i c a t i o n o f t h e r a t i o o f  deuterium concentration material.  t a r g e t , the r a t i o of the "equivalent  e r r o r , of these concentrations  concentration  T a b l e 3 i s a summary o f t h e a l p h a  indicates  ( i e a f t e r H e bombardment) o f d e u 3  i s t h e same f o r b o t h  f o r Carbon Layer  The agree^-  t h e " t h i n " and " t h i c k " t a r g e t s .  Variations yield  s t u d y c a r r i e d o u t on t a r g e t s  with  TABLE 3: TARGET  (C Di )n THICKNESS (yg/cm ) 2  t  2  A SUMMARY OF THE ALPHA Y I E L D STUDY ON TARGETS WITH DIFFERENT CARBON LAYER THICKNESSES  1st C LAYER THICKNESS (ON BACK) (yg/cm )  1st C LAYER THICKNESS (ON FRONT) (yg/cm )  NO. OF 10 y g / c m CARBON LAYERS ON BACK ON FRONT  2  2  2  " F I N A L ALPHA Y I E L D " AFTER 300 yC o f H e (COUNTS/0.9 y C ) 3  FACTOR INCREASE IN FINAL YIELD (RELATIVE TO FINAL Y I E L D FOR "BASIC SANDWICH" TARGET)  He BEAM CURRENT ( uA) 3  1 IAS (1)  38.0±5.8  10.Oil.7  8.0+1.4  1.0*0.17 1.0±0.17  170±13  1 .0  0.15  1 IAS (2)  38.0+5.8  10.0+1.7  8.011.4  3.0±0.26 1.OlO.17  930+13  5.47+0.60  0.18  1 IBS(l)  38.0±5.8  10.0±1.7  8.Oil.4  1 .0±0.17 1.0±0.17  195-1^  1 .0  0.12  1 IBS(2)  38.0±5.3  10.0+1.7  8.Oil.4  2.0±0.20 1.0l0.17  750128  3.84+0.42  0.12  1 IBS(3)  38.0+5.8  10.0+1.7  8.011.4  ii.OtO.28 1.oio.17  1375138  7.05±0.70  0.08  1 ICS (1)  40.016.0  10.Oil.7  8.011.4  i.oio.17 1.0+0.17  190ll3  1 .0  0.14  1ICS(2)R  40.0*6.0  10.0±1.7  8.0+1.4  •1 .0+0.17 4.0+0.35  1050132  5.52+0.54  0.09  1 ICS (3)  40.016.0  10.Oil.7  8.Oil.4  ^.010.35 1.oio.17  1350137  7.1+0.67  0.07  1 1 IBS (1)125.0+17.5  10.oil.0  11.0+1.1  3.oio.26 1.oio.17  2950154  1 1 1 BS (2)R125.0+17.5  io.oil.o  n.oii.i  i.oio.17 3.oio.26  2300±48  -  0.09 0.09  - 67  different  carbon  layer thicknesses.  " b a s i c sandwich" prising  targets  the "sandwiches".  "back"  and  on  layers  and  the e x t r a  of  initial  the  determined in  by  the t o t a l  evaporated  carbon  number o f  straight  line  in the  150  y c ) and  passed  the alpha y i e l d s  of  c o u n t s a t 300  c u r r e n t o f 0.9 convenience.  300  carbon  the f i n a l The  yc)  i s determined  carbon  the e r r o r  I t may  yc f o r w h i c h second  a straight  errors  uncertainty  i n t h e number  the preset  integrated chosen  for  increase  yield  when a d d i t i o n a l  l a y e r s o f c a r b o n have been added t o  error  f o r each  increase  e r r o r s of the f i n a l  carbon  layers.  For t a r g e t s  measured f o r the t a r g e t  alpha y i e l d  graph,  numbered c u r v e .  yields  i s t a k e n as t h e sum  the  of the r e -  f o r t a r g e t s w i t h and w i t h o u t t h e a d d e d  I I I B S ( l ) and  sandwiches  I I IBS ( 2 ) R , no y i e l d  without carbon  curves are displayed  the legend at the top Beside each  line  the  The  column o f T a b l e 3 g i v e s the f a c t o r  factor  •  stabilized  In a l l c a s e s  t h e a l p h a c o u n t s w e r e t a k e n , was  last  error  subsequent  "final  f l a g s of these values.  be n o t e d h e r e , t h a t  The  in the  d e c r e a s e had  the s t a t i s t i c a l  were  i s t h u s made  The  by f i t t i n g  the p l o t .  the  The t h i c k n e s s e s  f r o n t o r back  the alpha y i e l d  a r e t a k e n as  lative  each  initial  l a y e r plus the e r r o r  become l i n e a r on  through  yc.  The  com-  l a y e r s on  includes both the  l a y e r s on e i t h e r  initial  (after  in  For  carbon  t h e w e i g h i n g t e c h n i q u e d e s c r i b e d i n s e c t i o n 2.2.2.  value  by  actual  2  layers  l a y e r s o f c a r b o n as m e a s u r e d by t h e T m o n i t o r .  (usually  The  target  10 y g / c m  initial  the  l a y e r s on b o t h s i d e s o f t h e p o l y e t h y l e n e f i l m  those values o c c u r r i n g a f t e r  target.  table contains a l i s t of  l a y e r s added f o r t h e s t u d y .  number o f c a r b o n  alpha y i e l d "  in  The  carbon  The  the t h i c k n e s s e s of the  the " f r o n t " of each  up o f t h e e r r o r  to  and  -  target  layers  designation  was  added.  i n F i g u r e s 18,  indicates  curve  19, 20 and  the p a r t i c u l a r  target  are b r a c k e t e d symbols  21. by i t s which  10' 9  -  8 -  (1)  =  Target  I IAS (2) - (3CB)  (2)  =  Target  I I AS (1)  7 -  65  4-\  — O  o 3 O  o o u  3H  z4  A  I0 -  o  9 -  A  I  (I)  II  I  H  876-  a o  5-  < I  A  5  4-^  0-  I 10'  I  1  I  1  1  I I 1 I I II 1  I  0 10 2 0  50  100 TOTAL  FIGURE 18:  150 INTEGRATED  200  250  BEAM  CURRENT  ALPHA YIE L D AS A FUNCTION OF THE TOTAL TARGETS  I I AS (1) AND I IAS (2)  300  350  (^C)  INTEGRATED BEAM CURRENT ON TARGET FOR THE  CO  10  I  6  1  —I  T T  9 8 — 7 — 5i A- —  1  (1)  =  Target  I IBS(3) - ( 4 C B )  (2)  =  Target  I IBS(2)  (3)  =  Target  IIBS(l)  - (2CB)  0  io  o  U  e  o  o cn  o e o  t— z  o  6>  O 0  •  •  I  I  I  I  1  I  a A A  io _| 3  A  A  A  8•  O  A  A  !  I  I  I  I  I  7-1  I  1  *  I  (I)  (2) I  I  I  I  I  6 - 1 o %o  J  U J  <  .-I  Q.  3  o  o  ©  5  i  I  (3)  • 1 1 I I I I 1 I I  J__L  IO' 0  10 2 0  100  50  TOTAL FIGURE 19:  2 0 0  150  INTEGRATED  BEAM  ALPHA Y I E L D AS A FUNCTION OF THE TOTAL TARGETS  IIBS(l),  I IBS (2) AND  I IBS (3)  3 0 0  2 5 0  CURRENT  3 5 0  (yuC)  INTEGRATED BEAM CURRENT ON TARGET FOR THE  10*  T T  9 —  1  1  1  8 —  7  —  6 - 1 1  ^O  CD  6 cn • »z O  s Q  _l UJ  5-  (1)  =  Target  I 1 CS (3)  -  (4CB)  (2)  =  Target  I ICS (2)R  -  (4CF)  (3)  =  Target  IICS(l)  1^  6  Oo  6  .  (I)  A  A  A  A  IO:-H  I  *  I I  *  »  I  I * I I' I  I  I  I I  I  I  (2)  9 -  "  8  76-  < I  QL  543-  e o Z—  10'  ©  o  'in'  i i i i  (3)  H i i i  _L_L  0 10 2 0  100  50  TOTAL -F-l GURE 20:-  ALPHA YIELD TARGETS  AS A FUNCTION  MCS(l),  I ICS (2)R  200  250  BEAM  CURRENT  150 INTEGRATED  OF T H E T O T A L AND  I I CS (3)  300  350  {jxC)  I N T E G R A T E D . BEAM. C U R R E N T ON T A R G E T  FOR T H E  10'  T  i 6  T  (1)  =  Target  I I IBS (1)  (2)  =  Target  I  - (3CB)  —  5 -  I IBS(2)R - ( 3 C F )  4-  3 O  ^ 2-^  co rZ  Zi  o  o 9-# 87LU  8-  A A • *  O O  ©  &  < X  ^ A  *A A  OL  A A  1  io*  i  I  T  i  I  1  I  I  I  I  I  T  I  I I (|) i  i (2)  _L  _L_L 0 10 20  50  100  TOTAL FIGURE  I  i  2 1 :  ALPHA YIELD TARGETS  150  INTEGRATED BEAM  A S A FUNCTION  II IBS(1)  200  OF T H E T O T A L  AND II IBS (2)R  250  300  350  CURRENT (yuC)  INTEGRATED  BEAM C U R R E N T ON T A R G E T  FOR T H E  - 72 -  indicate eg  t h e number o f 10 y g / c m  3CB i n d i c a t e s  layers  on t h e f r o n t  sandwich" in  target  carbon  carbon  layers  l a y e r s on t h e back o r t h e f r o n t  on t h e b a c k ,  4CF i n d i c a t e s  e t c . Absence o f these symbols  with  these symbols  having several  as  3 carbon  2  one c a r b o n  (as i n a l l t h i s  carbon  layers  indicates  l a y e r on both back discussion)  on e i t h e r  l a y e r on t h e o p p o s i t e s i d e .  carbon  a  "basic  and f r o n t .  i s the fact  that  side of the target  Comments  k  regarding  Implicit a  always  target, has o n e  these curves are  follows: ( i ) The " b a s i c 1ICS(1) istics (ii)  sandwich"  target  show a l l t h e t a r g e t as d i s c u s s e d  The y i e l d  yield  curves  d e t e r i o r a t i o n and c u r v e  with  large  target  appears  early  a slow decrease targets.  layers  fluctuations  The a l p h a y i e l d  the y i e l d  number o f c a r b o n  on t h e b a c k  appears layers.  alpha y i e l d  multicarbon  An a n a l y s i s layer  o f t h e change  thicknesses  layers  decrease appears  layered  s u c h as s e e n  f o r the "basic"  sooner  targets  in "final  i s presented  to s t a b i l i z e  sooner  An i n c r e a s e d  number o f c a r b o n  on t h e f r o n t .  f o r an  the f i n a l  yield  The f i n a l  rate  t o be t h e same f o r b o t h " b a s i c " and  ( i e the f i n a l  slopes are p a r a l l e l ) .  alpha y i e l d s " with  i n Figures  and e x h i b i t s  than f o r t h e b a s i c  i s more e f f e c t i v e i n i n c r e a s i n g  t h a n t h e same number o f c a r b o n of  The ^ t a r g e t  decrease s t a b i l i z e s  ( l i n e a r on t h e g r a p h )  Moreover  increasing  60 t o 100 y c .  do n o t  t o be more u n i f o r m and d o e s n o t e x p e r i e n c e  relative  IIBS(l).  character-  multicarbon layers  d e c r e a s e as r a p i d l y o v e r t h e f i r s t  the  I I B S ( l ) and  i n 3 - 3 -1 -  curves f o r targets  deterioration  IIAS(l),  different  carbon  22 and 2 3 , w h e r e t h e d a t a h a s been  - 73 -  2000  1800  1600  6 in  1400  > — z 3  o o  1200  d  10001  < £  800|  600  400  200 100 0  1 No.  2  3  OF 10^ugm/cm*  FIGURE 22:  1  4  CARBON  5 LAYERS  6  7  ON TARGET  8 BACK  FINAL ALPHA YIELD AS A FUNCTION OF THE NUMBER OF 10 yg/cm CARBON LAYERS ON THE "BACK" OF THE TARGET  2  -  No. OF FIGURE  23:  10/igm/cm*  THERATIO LAYERS IN  OF T H E  ON T H E  -  CARBON "FINAL  OF C A R B O N  "BASIC" LAYERS  LAYERS  ALPHA  " B A C K " TO T H E  ITS ORIGINAL  NUMBER  Ik  YIELD"  "FINAL  SANDWICH  ON  TARGET  FOR A G I V E N  ALPHA  FORM,  YIELD"  BACK  NUMBER FOR T H E  A S A FUNCTION  OF C A R B O N SAME  OF T H E  TARGET  - 75 -  t a k e n f r o m T a b l e 3-  22  Figure  ( c o u n t s / 0 . 9 y c a t 300  i s a graph o f the " f i n a l  y c ) a s a f u n c t i o n o f t h e number o f 10  l a y e r s on t h e " b a c k " o f t h e t a r g e t . observed  points  p o s e d o f one 10  be  consistency roughly  error  yg/cm  carbon  2  (they  agree w i t h i n  of the three  target  i n t o account p o s s i b l e  Table 3 are presented for  a given  for  t h e same t a r g e t  the  number o f c a r b o n  in the final  flags of the points.  the  in Figures  22  beginning of this  t o an a v e r a g e f a c t o r carbon final  samples.  on  only  errors)  com-  The  close  indicates  The r e l a t i o n s h i p a p p e a r s t o  n o t be drawn b e c a u s e o n l y  23  p e r 10  one p o i n t  23  as a f u n c t i o n  i s therefore  the errors  section. increase  The o b s e r v e d i n the " f i n a l  a p l o t of the f a c t o r  carbon  (at k carbon  layers  the e r r o r  H e y i e l d " o f 1.83  The c o r r e s p o n d i n g  and y i e l d e d  1  at  corresponds t  0.35  factor  per  increase  l a y e r on t h e " f r o n t " o f t h e t a r g e t was  layers)  on  i n t h e number o f c a r b o n  l i n e a r dependence 4  yield"  function  i n T a b l e 3 and d i s c u s s e d  h a v e been l i s t e d  yield"  alpha  A s t r a i g h t l i n e may be drawn t h r o u g h  and 23  2  alpha  o f t h e number o f c a r b o n  I t may be n o t e d t h a t  yg/cm  the r e s u l t s of  " b a s i c " s a n d w i c h f o r m , as a  Figure  was  inconclusive.  l a y e r s on t h e " b a c k " t o t h e " f i n a l  layers.  yield  one p o i n t  as t h e r a t i o o f t h e " f i n a l  l a y e r on t h e b a c k o f t h e t a r g e t . yield  three  sandwich" targets  v a r i a t i o n s between t a r g e t s ,  in its original  "back" o f the t a r g e t .  layers  carbon  2  A corresponding graph f o r a v a r i a t i o n o f  in Figure  t h e number o f c a r b o n  increase  layer, the  the s t a t i s t i c a l  a v a i l a b l e and t h e r e s u l t w o u l d h a v e been  of  yg/cm  l i n e a r a n d i n f a c t a s t r a i g h t l i n e c a n be drawn t h r o u g h t h e  l a y e r s on t h e " f r o n t " c o u l d  To t a k e  yield"  l a y e r on t h e b a c k a n d on t h e f r o n t .  flags of a l l the points.  carbon  F o r one c a r b o n  are the alpha y i e l d s f o r the "basic  grouping of the points the  alpha  the value  1.38  t  in  based  0.26.  - 76  In a d d i t i o n "final  two t a r g e t s ,  alpha  I I C and 1 M B ,  y i e l d " with  a given  o r on t h e f r o n t o f t h e t a r g e t . target  180° w i t h  a new " s p o t " .  respect  number o f c a r b o n This  l a y e r s on t h e " f r o n t " was  that  Although  extending  1.29 t  thickness  on t h e f r o n t o f t h e t a r g e t . thickness  as  that  target  1MB  has  as t h i n n e r  2  poly-  layers.  explained  Beam  Profile o f Measurement Parameters  in section  at their  the c o r r e c t  2.5.2, i n o r d e r  to locate the alpha  kinematica11y corresponding angles,  location f o r the s o l i d  the o p t i m i z a t i o n  state detector  procedures are presented  the errors  the r e l a t i v e errors  Figure  I t may be n o t e d  the carbon  t h i c k e r as w e l l  In a l l c a s e s of  than e x t e n d i n g  i n t h e same manner f o r t a r g e t s w i t h  2.4.1 O p t i m i z a t i o n  of  yield"  t h e phenomenon  detectors  of  alpha  i s more  i n d i c a t i n g that  Proton  find  the " f i n a l  t h e y do s u g g e s t  125 p g / c m ,  ethylene  As  I I C and 1.28 ± 0.05 f o r  on t h e b a c k o f t h e t a r g e t  thickness  3.4  f o r a number o f c a r b o n  f o r t h e same number o f c a r b o n  0.07k f o r t a r g e t  in increasing  occurs  yield  yield"  these r e s u l t s a r e not c o n c l u s i v e ,  the carbon  ^ D i j n  alpha  alpha  effective  a poured  l a y e r s e i t h e r on t h e b a c k  was a c c o m p l i s h e d by r o t a t i n g t h e same  The r a t i o o f t h e " f i n a l  1MB.  f o r the  t o t h e i n c i d e n t beam d i r e c t i o n and i n v e s t i g a t i n g  l a y e r s on t h e " b a c k " t o t h e f i n a l  target  were each compared d i r e c t l y  i n t h e AC/C  in Figures  i t was n e c e s s a r y t o assembly.  f r o m t h e sum  counts.  24 i s a g r a p h o f t h e r a t i o o f a n t i c o i n c i d e n c e state detector  The r e s u l t s  2 4 , 25, 26 and 2 7 .  q u a n t i t i e s are determined  i n t h e AC and C s c a l e r  a function of the s o l i d  and p r o t o n  to coincidence  assembly angle.  counts  I t may be n o t e d  - 77 -  234  235  23B  237  238  SOLID S T A T E DETECTOR FIGURE  2k:  THE RATIO FUNCTION  OF A N T I C O I N C I D E N C E OF T H E S O L I D  STATE  239  ASSEMBLY  TO C O I N C I D E N C E DETECTOR  240  ANGLE (  COUNTS A S A  ASSEMBLY ANGLE  241 0  )  -  75  78  7.6  SOLID S T A T E FIGURE  25:  THE  RATIO  FUNCTION  OF A N T I C O I N C I D E N C E OF T H E S O L I D  STATE  -  7 7  7.8  DETECTOR  7.9  HEIGHT(cm.)  TO C O I N C I D E N C E DETECTOR  HEIGHT  COUNTS A S A  8.0  - 79 -  200  220  240  260  TIME FIGURE  26:  THE RATIO FUNCTION  280  320  340  D E L A Y I nanosec.)  OF A N T I C O I N C I D E N C E OF T H E T I M E  300  DELAY  TO C O I N C I D E N C E  FOR T H E PROTON  COUNTS A S  PULSES  A  80  i  r  I  r  i  i  r  Solid  State  Angle  =  T"  Detector  Assembly  240.5°  t.o  0.9  o.a-  0.7  \  \  0.6 O \  o <  \  0.5  I  \  \  \  0-4  \  \  0.3  keV Window  100 on  0.2  Alpha  Base  Peak  Line  Centered for  this  Setting  0.1  0.4 FIGURE  27:  THE  0.8 RATIO  FUNCTION  J  1.2  L  _L  BASE  1.6  J  LINE  OF A N T I C O I N C I D E N C E OF T H E B A S E  LINE  L  2.0  J  2.4  L  SETTING  TO C O I N C I D E N C E  SETTING  2.8 COUNTS  J  3.2 AS A  FOR T H E 1 0 0 k e V WINDOW  L  3.6  - 81  that  the angular  angles  steps  2 3 7 - 5 ° and  and  the  point.  taken.  c u r v e was  This  The  F i g u r e 25  t h e AC/C  d e t e c t o r h e i g h t where t h i s relative  to the plane  detector.  The  r a t i o as  height  defined  by  minimum p o i n t on  symmetric about a v e r t i c a l  the curve  0.5  cm  (i£.  thereby  the  the v e r t i c a l  a t 7-7  0.2°.  cm  the and  point.  locating  state  position  the a x i s of  this  96.2°)  actually  solid  occurred  at  through  a f u n c t i o n of  beam and  3  -  l i n e drawn  -  i s d e f i n e d as the He  occurred  located at 237-5°  l i n e drawn t h r o u g h  p o s i t i o n e d a t 7.7  d e t e c t o r was  the curve  c o r r e c t angle  temporarily  are  to accurately define  symmetric about a v e r t i c a l  i s the kinematica11y  i s a graph of  c o r r e c t but  serve only  minimum p o i n t on  t h e d e t e c t o r a s s e m b l y was  was  kinematica11y  p e c u l i a r t o t h e chamber u s e d and  the a n g u l a r  this  numbers u s e d a r e n o t  -  proton the  curve  The  alpha  i t i n the  plane  defined.  F i g u r e 26  i s a graph of  nanoseconds) where t h i s As  those flat of  pulses of  of  a f u n c t i o n of  the  is adjusted  at the proton  channel  to  locate their  i t was  r e g i o n 70  pulses.  nanoseconds wide.  time the  the " f a s t "  d e l a y was  flat  region.  c h o s e n as  This  pulses 265  The  to delay  minimum o f  limited  used  i 0.5  time  delay Timing  SCA'.  same t i m e  t h e g r a p h was  i s due  as a  t o the r e s o l u t i o n  resolution results  in the " f a s t  (in  the " c o i n c i d e n t "  p o i n t s at the  This wide v a l l e y  the " c o i n c i d e n c e " e l e c t r o n i c s . of  necessary  "zero-crossover"  the " c o i n c i d e n t " alpha  from the w i d t h The  delay  r a t i o as  in section 2.5-2,  explained  proton  t h e AC/C  coincidence"  nanoseconds c o r r e s p o n d i n g  partially electronics.  to the  centre  - 82 -  F i g u r e 27 setting  i s a g r a p h o f t h e AC/C  on t h e a l p h a  state detector several  channel  r a t i o as a f u n c t i o n o f t h e base  Timing  (S.S.D.) a s s e m b l y .  angular  SCA f o r a g i v e n a n g l e o f t h e s o l i d T h i s m e a s u r e m e n t was  assembly.  as a f u r t h e r c h e c k o f t h e a n g u l a r F o r F i g u r e 27 t h e AC/C  o f 2.0 t  setting  on t h e a l p h a the  performed f o r  p o s i t i o n s o f t h e S.S.D. a s s e m b l y w h e r e t h e AC/C  was m e a s u r e d w h i l e s w e e p i n g t h e 100 keV w i n d o w a c r o s s This serves  line  S i n c e t h i s was  S.S.D. a s s e m b l y  a t a base  t o t h e 100 keV w i n d o w  t h e opimum c o r r e l a t i o n ,  (240.5° - 0.2°)  peak.  p o s i t i o n o f t h e S.S.D.  r a t i o minimum o c c u r r e d  0.5 w h i c h c o r r e s p o n d e d  peak.  the alpha  ratio  was a c c e p t e d  line  centered  this  angle of  a s t h e c o r r e c t one  kinematically.  3.4.2  Horizontal Profile  F i g u r e 28 p r e s e n t s The " o b s e r v e "  profile  method d e s c r i b e d were determined collimator  three separate  horizontal  i n s e c t i o n 2.5.  For t h i s  d e v i c e and n o r m a l i z i n g t h e s e  relative  e r r o r s o f t h e C and  were p l o t t e d  the p o s i t i o n  ratios  were determined In t h i s  t o a peak  direction.  these  measurements were  case  the absolute e r r o r of the  The  relative  from the c e n t r e o f the  These angles  were determined  and t h e c o l l i m a t o r in effect,  intensity  f r o m t h e sum o f t h e  t o t h e s q u a r e r o o t o f t h e sum  of the c o l l i m a t o r opening  However  intensities  f o r each p o s i t i o n o f t h e  as a f u n c t i o n o f t h e a n g l e  beam i n t h e h o r i z o n t a l  beam.  d e v i c e and  the r e l a t i v e  o f t h e a b s o l u t e e r r o r s i n t h e C and AC c o u n t v a l u e s .  intensities  tance.  intensity  (C + AC) c o u n t s .  t h e (C + AC) c o u n t v/as e q u a t e d  proton  profile  by m e a s u r i n g t h e r a t i o C/(C + AC)  The e r r o r s i n t h e i n t e n s i t i e s  squares  of the proton  i s t h e one m e a s u r e d u s i n g t h e c o l l i m a t o r  o f one.  of  profiles  from  to t a r g e t spot  determining  dis-  an i n t e g r a t e d  - 83 T Profi1e  i-oh  T  from  Previous  Work  Observed  Prof i l e  "True"  (Ho 6 8 )  Profile  0-9  OQl  07  t  (ft  0-G\  Z UI Iz  0-5I"  > £  o-4  03r  0-2  Ol  ' 1  -8° FIGURE? 28:  ±4*•6°  JZ> ' -5° -4*  HORIZONTAL  . ° _ ° _j° ° +.1° +2° +3° +4° +5° +6° +7° +8° ANGLE FROM BEAM CENTER 3  PROFILES  2  OF PROTON  0  BEAM  - 84  profile finite  s i n c e the c o l l i m a t o r opening  0.125".  diameter of  p o i n t being chosen the  integrated  collimator  are  Hence t h e o b s e r v e d  i n t e n s i t y over the complete Since the p r o f i l e  process w i l l  e f f e c t , an " i n t e g r a t i n g by f i r s t  assuming  that  not p r e s e n t e d here  on e i t h e r  integrated  intensity  p r o c e s s " was i t was  carried  new  "integrated  in graphical  subtends  form).  wider than the observed  the  "observed" p r o f i l e  the p r o f i l e  The  method, t h e " t r u e " p r o f i l e  profile  ice  D0 2  the "observed"  this profile test  each  a  observed  c u r v e and  point,  vertical  lines  t a k e n as  was  a h a l f angle of  1.85°  at the t a r g e t .  profile.  The  was  narrowed  i n t h e f i g u r e was  coincided with  because  and  profile  integrating  effect,  by an amount e q u a l  As  These  constructed  of the " c o n s t r u c t e d " p r o f i l e . the graph.  chosen  the  i n t e n s i t y o f one  To a l l o w f o r t h i s  d e s c r i b e d (i.e. c a l c u l a t i n g  "constructed" profile  test  1.85°  d e s i g n a t e d t h e " t r u e " p r o f i l e on  The  To  an  figure  o f F i g u r e 28  measured s p r e a d i n g e f f e c t  the  circular  ( the r e s u l t s of the  the " o b s e r v e d " p r o f i l e .  was  firming  For  (the  is actually  s h a r p , such  i n t e n s i t i e s " were n o r m a l i z e d t o a peak  on a d i a g r a m w i t h  process j u s t  o u t on  the " t r u e " p r o f i l e  f o r the p o i n t .  c o l l i m a t o r opening  was  s u r f a c e of the  is relatively  a  at a point  s i d e o f t h e a n g u l a r p o s i t i o n o f t h e p o i n t was  the  plotted  intensity  tend to widen the " t r u e " p r o f i l e .  m e a s u r e m e n t o f t h e a r e a b o u n d e d by 1.85°  i s n o t o f a t o m i c s i z e b u t has  as t h e c e n t r e o f t h e c o l l i m a t o r o p e n i n g )  opening.  integrating  -  T h i s new  to  profile  a c r o s s check of  s u b j e c t e d t o t h e same  t h e a r e a s e t c . ) , and  the "observed" p r o f i l e  the  the  this  integrating  resultant  thereby  con-  procedure.  from p r e v i o u s work  copper  backed  (Ho 68)  r e p r e s e n t s the r e s u l t s  t a r g e t as e x p l a i n e d i n s e c t i o n  1.1.  using a  solid  As e x p l a i n e d i n  - 85 -  2.5.2  section  attenuation positions In  this  (via  of  case  profile  of  relations  (and  the  in the  the  results  ratio  solid  Hojvat  AC/C)  state  the  proton  beam.  (e.g.  see  Figures  as  used  the  2 and  he was  3)  position  of  the  in  the  angular  position  of  the  proton  for  the  horizontal  of  ice  heavy  parison  of  "previous  for  work"  by  59%  carbon  width  profile  by  of  The  full  spreading  the  (i.e.  by  backed  target.  width,  the  and  a factor  of  measurements,  could  also  reduced  protons  subtended  3.4.3 Figure  scattered by  the  Vertical 29  by in  a  2.43),  the  the  should  the  target  the  part  of  this  of  the  implies angle  rather  of  The  backing  into  be <5  x  angles 5  A com-  and  the  copper  This  8.5° implies  reduced  self-supporting  future the  proton  proton  reaction  detector  attenuation,  larger  as  10~  change  was  0.5,  the  resulting  shift  scattering  the  beam was  by  change  a  elastic  of  for  subtended  by  profile  than  proton use  a  (Ho 68)].  profile.  that  2.43-  still  run"  reduced  angular  kinematical  produced  intensity  the  the  it.  assymetry  "true"  "true"  through  solid  carbon  of  relative For  3-5°  a factor  detector,  than  desired  due  those  (see  .  section  Profile  presents  measurements  at  Therefore,  section  to  indication  horizontal  cross  be  an  was  the  position  corresponding  particular  maximum" o f  self-supported  profile of  half  vertical  translate  that"the  profile  that  to  and  to o b t a i n  to  the  [note  the  reaction's  able  into  beam  during  at  was  use  "previous"  the  thickness  "full  target.  the  that  target  the  accomplished backed  figure  detector  of  angular  used  3  angular  in the  were  H ( He,p)^He  2  the  observed  He  the  measurements  in  4  of  assembly  these  Using 1,  measurements  a function  detector  also  (68)  3-4.1),  in  are  three  from  the  separate same  vertical  sources  as  p r o f i l e s of described  the  for  proton  the  beam.  horizontal  The  1.1).  - 86 -  lOh  ANGLE FIGURE  29:  VERTICAL  FROM PROFILES  BEAM OF PROTON  CENTER BEAM  - 87 -  profiles the  (section  initial  3.4.2).  "steps"  In t h i s  case the r e s u l t s a r e i n c o n c l u s i v e  taken about t h e proton  d i r e c t i o n were t o o l a r g e t o d e f i n e vertical  beam c e n t r e  the p r o f i l e  p r o f i l e was s o n a r r o w t h a t  beam c e n t r e .  on a p o i n t  3-70°  f r o m t h e beam c u r r e n t )  An " i n t e g r a t i n g p r o c e s s "  (as d e s c r i b e d  p r o f i l e ) was c a r r i e d o u t o n t h e " o b s e r v e d " p r o f i l e profile. proton  The o n l y  conclusive  beam p r o f i l e The v a l u e  "previous"  profile  by  "at least"  (i.e.  on e i t h e r s i d e o f t h e f o r the horizontal  yielding  r e m a r k t o be made i s t h a t  of the " f u l l  width  as compared w i t h i n the spreading  3.2°  i s , the  the opening  the " t r u e "  the actual  i s a t l e a s t a s n a r r o w as t h e " t r u e " p r o f i l e  narrower.  implies a reduction  That  i n t e n s i t y was r e d u c e d t o  z e r o when t h e c o l l i m a t o r o p e n i n g was moved o n e " s t e p " was c e n t e r e d  in the v e r t i c a l  accuractely.  the r e l a t i v e  since  vertical  and may be  a t h a l f maximum" was 6.7°  f o r the  f o r the "true"  This  of the v e r t i c a l  profile.  part o f the proton  52% t h r o u g h u s e o f t h e s e l f - s u p p o r t i n g t a r g e t s .  beam  - 88 -  CHAPTER IV  CONCLUSIONS AND SUGGESTIONS  h. 1  General  Conclusions  (C Dt )n "sandwich" t a r g e t d e s i g n , developed  The  2  while  f  in solution,  targets  described  in this  the evaporating  higher success  (C Di )n 2  +  rate f o r stripping  They b o t h  thickness  to a  and m o u n t i n g .  losses.  p r o d u c e d t h e most a c c u r a t e  carbon  l a y e r s o f both  design  involving  design  i n v o l v i n g evaporated  designs.  The p o u r e d a n d  2  i s a b e t t e r process  t o 1% t h r o u g h  t |  the l a t t e r  thickness.  a b e t t e r weighing  g e o m e t r y as e x p l a i n e d  The  t e s t i n g on " c r o s s - 1 i n k i n g " o f t h e ( C D ) n  the t a r g e t s .  in their perforcurves,  resonator  thickness determinations  evaporation  gamma r a d i a t i o n  evaporated  t o produce as r e g a r d s t o  The u s e o f a q u a r t z  polyethylene, although  6% more a c c u r a t e m e a s u r e m e n t s o f t h e ( C D ) n  limited  as t h e  f o r the  The c o n c l u s i o n i s t h a t t h e " s a n d w i c h " t a r g e t  pouring o f the polyethylene  f e r e n c e w o u l d be r e d u c e d  as w e l l  H e beam a s m e a s u r e d by t h e i r a l p h a y i e l d  l o s s e s and d e u t e r i u m  thickness monitor  difficulty  +  a p p e a r t o be e q u a l l y e f f e c t i v e 3  economical  i s p r i m a r i l y due t o t h e l a r g e r number 2  mance when s u b j e c t e d total  This  those  In a d d i t i o n , t h e p o u r i n g  ( s e c t i o n 2.2.2) i s 83% more  thesis  t a r g e t s a r e e s s e n t i a l l y o f equal  t i m e and e f f o r t .  s t r o n g e r t a r g e t s than  the polyethylene.  technique.  the polyethylene  produced f o r a given q u a n t i t y o f (C Di )n  of "poured" t a r g e t s 65%  in mechanically  p r o d u c e d by e v a p o r a t i n g  technique than  results  by p o u r i n g  in section  process  process  enables  This accuracy  dif-  technique  carbon  and  3-2.  2  indicates that this  than t h e  i +  polymer chains  may be e f f e c t i v e  through  in strengthening  - 89  Carbon  l a y e r s evaporated onto both  mechanical  rigidity  conductivity. of  the  target that  yA/cm  2  Their  main  m o l e c u l e s as  C2D4  stability.  the  to the  The  50  f o r one  2  the  targets  All  the  basic  as  the  initial  of  total  slow alpha  have w i t h s t o o d  b o t h 45  thermal  the  film  carbon  evaporation  thereby  layers  5 to  10  destruction  or  decrease.  beam c u r r e n t  and  2  e v a p o r a t e d ) , e x h i b i t the  Moreover,  densities  of  undamaged a p p e a r a n c e  even g r e a t e r  yg/cm  providing  i s such  d e n s i t i e s of  yield  resulting relatively  integrated  3  He  yield  of  the  i n the  alpha  beam c u r r e n t  large deuterium  loss of  up  135  of  beam d e n s i t i e s .  yg/cm  thick  2  same t a r g e t d e t e r i o r a t i o n  large discrepancy implies  on  almost  target 100%  between the that  broken  a  large  of  thickness this  fraction  into their  of  150  total of  c a r b o n and  reflecting  30  t o 40%  target  the  t o 200  150  yc  an  yc w i t h  l e s s t h a n 0.05%  loss occurring  loss of  first  93%.  e x h i b i t i n g a slow decrease of  total  over the  target,  d e t e r i o r a t i o n between  i n the  yc w i t h  yield  to  A  t a r g e t were f i r s t  the  beam c u r r e n t  s u b s e q u e n t beam b o m b a r d m e n t ,  deuterium  and  inhibit  polyethylene  during  300  they  did withstand  rapid decrease  Stabilization  loss  electrical  follows:  An  alpha  of  h o u r and  ( p o u r e d and  initial  The  targets  as  film offer  t  measurements) w i t h o u t  typical  "sandwich", t a r g e t s of  characteristics  (iii)  the  the  i n d i c a t e d they could  polyethylene  (ii)  in the  2  e f f e c t of  to withstand  (during  (C Di )n  the  is that  a whole from the  hours  isolated tests,  yA/cm  (i)  importance  strengthening  w i t h o u t a marked change during  sides of  t a r g e t s , as w e l l  t a r g e t s were a b l e  for several  -  CgD^  per  over the  i n the  first  material  and  molecules  in  d e u t e r i u m components  the yc  first 150  the the by  yc.  loss  - 90 -  interactions with  the He  beam.  3  T h i s process then  f r a c t i o n o f d e u t e r i u m atoms d i f f u s i n g the  in  the i n i t i a l  the target  target  could  deterioration,  be p a r t l y  f o r m o f d e u t e r i u m atoms  target  indicate  that  m o l e c u l e s seems comparison the  "final  l a y e r s on e i t h e r  remaining i n the  in the t a r g e t . increasing  the "back" or the " f r o n t " o f the of the deuterium from  in the carbon.  It i s suggested  o f t h e t e s t s on " t h i n " and " t h i c k "  deuterium migrates throughout  i n the carbon  alpha y i e l d s " with  indeed a large f r a c t i o n  t o be t r a p p e d  i n the target.  C^D^form and p a r t l y  (or molecules) trapped  thickness o f the carbon  large  t h e d e u t e r i u m atoms s t i l l  i n the o r i g i n a l  The o b s e r v a t i o n s o f t h e i n c r e a s e d  in a  o u t o f t h e t a r g e t s w h e r e a s most o f  c a r b o n atoms f r o m t h e p o l y e t h y l e n e r e m a i n e d  After  resulted  targets  t h e t a r g e t and  the  (from the  in section  3-3.1)  a c o n c e n t r a t i o n o f 0.11  If  t h e d e u t e r i u m a t o m s m i g r a t e by an a p p r o x i m a t e l y i s o t r o p i c d i f f u s i o n increase  the  carbon  23  alpha y i e l d "  i n the target  carbon  2  age f a c t o r layeron  1.38  d e u t e r i u m atoms p e r c a r b o n  sandwich.  (the r a t i o o f the " f i n a l  10 y g / c m  on  in "final  t  individually  in the " f i n a l  resulted per carbon  in a factor  a l p h a y i e l d " o f 1.83 Similar increase  l a y e r on t h e f r o n t .  f o r comparison  back and f r o n t  dependenceof F i g u r e  a l p h a y i e l d s " a s a f u n c t i o n o f t h e number o f  the back o f the t a r g e t .  0.26  linear  only,  of the l o c a t i o n of  l a y e r s on t h e b a c k o f t h e t a r g e t ) c o r r e s p o n d e d  increase  the front  atom.  s h o u l d be i n d e p e n d e n t The o b s e r v e d  that  i s t r a p p e d by t h e c a r b o n  to  the  C2ni4  of the " f i n a l  carbon t h i c k n e s s v a r i a t i o n .  testing  - 0.35  f o r carbon  i n the " f i n a l In a d d i t i o n alpha y i e l d " The " f i n a l  t o an a v e r -  per carbon layer  variation  alpha y i e l d " of t a r g e t s were  tested  i n c r e a s e s f o r both alpha y i e l d "  per carbon  - 91 -  l a y e r was c o n s i s t e n t l y l o w e r f o r t h e l a y e r s on t h e f r o n t o f t h e t a r g e t s a s compared w i t h  t h o s e on t h e back.  Although  t h e y s u g g e s t an a d d i t i o n a l p r o c e s s o t h e r the  isotropic diffusion of  parameters f o r the e l a s t i c  on d e u t e r i u m a n d a c o n s i d e r a t i o n target  material, yielded  thickness  the following r e s u l t :  e n e r g y o f 552 keV ( t h e s c a t t e r e d to a "forward  was a p p r o x i m a t e l y material  five  amount o f momentum the  target  terium  times g r e a t e r  and t h e r e f o r e  atoms w i t h i n  the  desired  "final  t h i c k carbon  this  experiment  ments), the target energy  inthe target  kinematica11y  t h a n t h e amount o f t a r g e t that  with  have a  t o them w o u l d be s c a t t e r e d  atom  stopping significant  competely out o f  t o the migration  o f t h e deu-  the target.  r e s u l t s o f the carbon  very  H  2 4 . 2 ° ) , t h e r a n g e of t h i s  would not c o n t r i b u t e  The  high  2  a t an a n g l e o f 2k.2°  Hence d e u t e r i u m atoms  transferred  3  based on t h e l a r g e s t  d e u t e r i u m atoms w e r e  cone" o f h a l f - a n g l e  "presented" to i t .  s c a t t e r i n g o f He  o f t h e ranges o f t h e s c a t t e r e d  u s e d and t h e d e u t e r i u m a t o m s c a t t e r e d  restricted  of  than merely  d e u t e r i u m atoms w i t h i n t h e t a r g e t .  A c a l c u l a t i o n of the kinematic  an  these r e s u l t s are not c o n c l u s i v e ,  layer v a r i a t i o n study suggest  alpha  layers  yield"  could  be o b t a i n e d  in the "sandwich" target.  (and f u t u r e thickness  l o s s f o r a 690 keV  total  proton  that  a target  through  However  reaction cross  with  the use o f  f o r the purposes section  experi-  i s l i m i t e d by t h e r e q u i r e m e n t o f a 100 keV  He beam, as e x p l a i n e d  in section  1.1 f o r g o o d  p r o t o n beam c o l l i m a t i o n .  Previous using  measurements  (Ho 68) i n t o t a l  a copper backed heavy  ice target,  proton  reaction cross  required  section  the proton detector  studies, t o sub-  - 92 -  tend  a. ha.l.f. ang.le o f . l l °. a t . t h e t a r g e t . r  attenuation copper The  f  -S o f t h e . p r o t o n beam, due t o t h e p r o t o n s  into angles  larger  than  use o f a s e l f - s u p p o r t i n g  required  11°,  carbon  backed  scattering  cross section  for C(p,p) 1 2  backing layer, thickness o f  1 2  (C D )n 2  t +  target  By i n t e g r a t i n g C  20  so-that the  scattered  was < 5 x 1 0 ~ 5 as d e s i r e d  angle of the proton detector.  a carbon  The angle-was chosen  i n the  (see s e c t i o n  s h o u l d reduce  1.1).  this  the d i f f e r e n t i a l  [ w h e r e E (p) = 1 5 . 2 MeV] a n d u s i n g yg/cm ,- t h e a t t e n u a t i o n , 2  6, due,.to.  scattering of, the. protons by this .carbon -layer, was c a l c u l a t e d . f o r d i f f e r e n t v a l u e s o f t h e ha 1 f - a n g 1 e 6 s u b t e n d e d presented  i n Table  /.'-Tr  •••  ,  ,  H lo  if:  .  ••  .  : „ a.  The r e s u l t s a r e  4.  TABLE 4 : ,  by t h e p r o t o n d e t e c t o r .  A t t e n u a t i o n 6 o f t h e P r o t o n Beam (due t o S c a t t e r i n g ) f o r D i f f e r e n t Half Angles 6 S u b t e n d e d by t h e P r o t o n D e t e c t o r .  ,Ha\ft-Arjg.1 e_ e . . . . . . , • t  " 4°  i  A t t e n u a t i o n :<5; ; . •  (  '  5.50  x 10  5  6°  5.12 x 10"  7°  4.95 x 10"  8°  5  5  •  4.80 x 10"  5  '4.48 x IO"  5  ;.•  It  }..•  ;•  .•  .•  20°'  is illustrated 5  from  11°  d e t e c t o r would  to 7°-  3.15 x'10~  •-  i n the table  6 < 5 x 10 , the h a l f duced  R ;  5  that  t o achieve the requirement o f  angle subtended Consequently  be r e d u c e d  by t h e p r o t o n d e t e c t o r c o u l d be r e -  the s o l i d  by a f a c t o r o f 2 . 4 7 .  angle subtended This result  by t h e p r o t o n  agrees f a v o u r a b l y  - 93  with  the  r e s u l t s of  3.4.2).  section  the  The  beam, c o m p a r e d w i t h  tector could still  2.47  (as  proton  be  r e d u c e an the  retained.  rate of  A  This  f l u x of  represents  and  the  solid  10  S  3  by  t o 0.63  proton  a copper the  a n g l e by  the  backed  proton  2.47.  This x  a factor increase  68)  10  5  background  10  would  S  3  1  .  Accord-  " p a r a l y z a b l e dead  (Ho  de-  a f a c t o r of  non-coincident  t o 28.3  1  [see  by  the  condition 6 < 5 x  a f a c t o r of  x  of  using  the  reduce the  transmitted  f r o m 0.35  obtained  2.43  by  70  spreading  (see  time"  for this functional,  i n the  coincident  count  1.80.  8 to  10  hours of  3  He  (C Di )n 2  1.0  under s i m i l a r  conditions.  i n the  H e n c e , use  x  count  of  provide  t  the  quent a l l o w a b l e  10  3  yA  r a t e due  (C Di )n 2  count  thickness  +  compared w i t h  coincident  bombardment a t beam c u r r e n t  coincident  2  [where the  would  detector  measurements  angle subtended  reduction of  counts  increased  uA/cm , the  able  solid  a f a c t o r of  the  f r a c t i o n of  relationship].  10  the  r e d u c e d by  i n c i d e n t on  be  i n the  horizontal profile  incident proton  gate would  After  the  reduction  c a l c u l a t e d above) would a l s o  flux  ingly,  be  horizontal profile  observed  (H068), implied that  target  would  proton  -  was S  1  rate using  1  This  45  greater  2  the  increase  by  a f a c t o r of  target  usage)  I0  3  a factor  the  yA  1  ice  increase of  heavy  angle subtended  i n the  3.5  1  by  as  target 1.7  in  the  avail-  ice target.  the  proton  count  rate  the  subse-  detector  (as c o m p a r e d w i t h  coincident  S  target  d e u t e r i u m atoms  t t  of  ice copper-backed  x  ( C D ) n " s a n d w i c h " t a r g e t and  reduction  an  1.7  number o f  compared w i t h  self-supporting  was  "sandwich"  copper-^backed heavy  represents  to the  t a r g e t as  2  f o r the  (C^DiJn  the  yg/cm ]  d e n s i t i e s of  the  heavy  transmitted  - 3k  through  the "dead  time  measurements, t h i s t h e e r r o r s t o 57%  gate".  For  -  total  proton  reaction cross section  i n c r e a s e i n the c o u n t i n g would of the previous experimental  result  errors  in a reduction of  (Ho  68)  a t t e n u a t i o n d i f f e r e n c e m e a s u r e m e n t s f o r t h e same " r u n n i n g certainly  in the c r o s s s e c t i o n v a l u e s would  t h e same " r u n n i n g  time".  4.2  for Further  The  Suggestions r e s u l t s of  this  thus  be  t h e s i s warrant  further total  [as d e v e l o p e d  by  C.  Hojvat  (Ho  ments t h e u s e  of a self-supporting deuterated  target  (C i+)n  [ of a  certainty It  carbon  (based after  on 300  represent  t h i c k n e s s equal  that the p o l y e t h y l e n e  l a y e r on  both  the experimental yc of a  extended  100  3  r e s u l t s of  He  bombardment, t h i s  keV  energy  investigation  loss  of  proton  needed.  several  interesting  be  Is t h e r e an extra  (if)  pursued.  How  carbon  would  upper  A few  43%  un-  for  reaction cross  68)].  For  yg/cm ] would 2  l a y e r be  this  l a y e r s , and  and  "coinci-  these  enclosed  thesis,  "sandwich" reduce the  i n a 20 alpha  i t can  be  3  He  layers  ( i n the  questions  t o the g a i n  time". 2  yield" shown t h a t will  beam as d e s i r e d ) .  by  the  increased  target "sandwich"), i m p l i e d by  the  "final is  results  follows:  t h a t can  i f so a t what c a r b o n  alpha y i e l d "  un-  yg/cm  "sandwich" target material keV  measure-  f o r t h e same " r u n n i n g  o f t h e s e a r e as  limit  the " f i n a l  by  technique  t h e phenomena, r e f l e c t e d  carbon  which should  The  polyethylene  by 43%  t o a 690  thicker  There are  time".  reduced  s i d e s to i n c r e a s e the " f i n a l  alpha y i e l d s " with  (i)  t o 45  in the cross s e c t i o n values  i s suggested  thick  An  n  2  the  Study  s e c t i o n measurements u s i n g the a s s o c i a t e d p a r t i c l e dence e l e c t r o i c s "  of  be  achieved  by  thickness?  be a f f e c t e d , i f v e r y  thin  adding  - 95 -  (0.1 the  to 2 yg/cm ) i n i t i a l 2  "sandwich"  carbon  incorporated  in  target?  ) What a r e t h e m e c h a n i s m s by w h i c h and  l a y e r s were  the deuterium appears  to migrate  i s t r a p p e d by t h e c a r b o n ?  ) Would a t a r g e t carbon produce formance,  composed o f a l t e r n a t i n g l a y e r s o f  (C Di )n 2  the optimum r e s u l t s , as r e g a r d s t o t a r g e t  i n view of the observed  phenomenon?  t  and  per-  - 96 -  BIBLIOGRAPHY  Ar  66  G.T.  Ca  69  Canberra  De  69  D e u t e r a t e d p o l y e t h y l e n e (>S8% D) o b t a i n e d Dohme o f C a n a d a L t d . , M o n t r e a l , Q u e b e c .  El  69  Eldorado  Ho  68  CF. CF.  H o j v a t , N u c l . I n s t r . and M e t h . 66_ ( l 968) 13 H o j v a t , Ph.D. T h e s i s , U n i v e r s i t y o f B r i t i s h C o l u m b i a  Ko 66  E.H.  Kobisk,  Ku 55  W.E. K u n z , P h y s . Rev.  Arnison, Nucl.  M e t h . 40_ (1966) 359.  I n s t r . and  I n d u s t r i e s , 50 S i l v e r  Electronics,  S t . , Midd1etown,  Berkeley,  Nucleonics  24 (1966)  Maxman, N u c l .  Ma  69  R.D.  Mathis  Nu  60  N u c l e a r D a t a T a b l e s , P a r t 3 (i960), e d . Academcy o f S c i e n c e s , N a t i o n a l R e s e a r c h  Nu  69  Nuclear  I n s t r . and  I n c . , P.O. Box  Or  Oak R i d g e T e c h n i c a l  69  P r 67  Progress  M e t h . 50. (1967) 53-  2840 G u n d r y A v e . ,  M.A. O l i v o and  (1967) -  97 (1955) 456.  S.H.  01 67  and  122.  67  Data  from Merck, Sharp  California.  Ma  Co.,  Connecticut.  CM. Bailey,  451,  L o n g B e a c h , C a l i f o r n i a 90806. J.B. M a r i o n ( N a t i o n a l C o u n c i l I960).  Palotine,  Nucl.  Illinois  I n s t r . and  6OO67.  M e t h . 57. (1967) 353-  E n t e r p r i s e s C o r p o r a t i o n , Oak R i d g e ,  in Polymer Science  Vol  1, e d . A.D.  Jenkins  Tennessee.  (Pergamon  P r e s s 1967). SI 69  Sloan  T r 67  G.E.  Instruments T r i p a r d and  Co., B.L.  Santa  Barbara,  W h i t e , Rev.  Wh  58  W. W h a l i n g ,  Wh  65  M. W h i t e , Vacuum ]5_ (1965) 449.  Ya  62  L. Y a f f e , A n n u a l  Handbuch. d e r  Rev.  Physik  California.  Sci. Instr.  38. (1967) 435.  ( S p r i n g e r - V e r l a g , 1958, r e v 1962).  o f N u c l . Sc.  12 (1962) 153-  - 97 -  APPENDIX A  (C DiJn  THICKNESS REQUIREMENT  2  The  thickness of the (C D )n f i l m 2  is required  [ +  energy  l o s s t o an  yg/cm  i s c a l c u l a t e d from a c o n s i d e r a t i o n of the atomic  2  stopping  i n c i d e n t 690  keV H e 3  s e c t i o n s e f o r He  cross  3  ( He)  z  3  2  The  a 100  required  keV  thickness  (or  molecular  i n (C D )n.  3  To d e t e r m i n e t h e e f o r H e , we  beam.  to represent  2  [ +  use t h e r e l a t i o n  from  (Nu  60)  e (proton)  E/3 where z  2  from  f o r an E o f 690  f o r e from  The v a l u e s For  (Nu 60)  (Wh 58)  are  e( He)  carbon:  is z  2  =  3.11  s  =  3  keV  3.11  x  E(proton)  230 keV  690 keV  For  e( He)  hydrogen:  3  =  3.1 1 x 12 x I O "  =  3.11  230 keV =  E  f o r the molecular mol  .'. f o r a C DL. 2  (  X  n  Y  m  stopping  n e(X)  )  3.H  x  cross  3.4 x 10  2 x E(C) + 4 x e ( H )  • 15  section of  , + m e(Y) ^ atom atom  molecule:  £(0201,) =  cm-" atom  x e(proton)  690 keV  In g e n e r a l ,  —  1 5  £V  _  cm  2  atom  compounds,  -  and  98 -  f o r a n i n c i d e n t H e beam o f 69O k e V , 3  e(C U ) 2  k  =  2 x 3.11 x 12 x 1 0 "  -  116.936 x 1 0 - 1 5 « V  1 5  + 4 x 3.11 x 3 . 4 x 1 0 "  1 5  f  c  molecule For  a polymer chain  (C Di+)n w h o s e d e g r e e o f p o l y m e r i z a t i o n  of  2  mined by t h e s u b s c r i p t n, t h e m o l e c u l a r e[ (C Di )n] 2  Recalculate ev  For  4  =  n x e (C9.D4)  =  n x 116.936 x I O "  e i n terms o f ev - c m - cm gm J this  —  n x E(C DI ) x 2  e (C Du) 32  AE  e  0  t h e energy  +  n  i n gm/cm  [ +  (ev) = (ev - cm2/gm)  C  material  o f molecules gm  ^^2  ^  5  e v by e  Q  1 0 x 32 e(C D ) x A 5  2  T T  5  =  '  2  10 x 32 I 16.936 x 1 0 "  .'.the r e q u i r e d  x  l o s s A E = 100 keV = 1 0  of (C D )n 2  ~ ? m o i e c u 1e V  45.5 x 10"  thickness  =  Avagadro's  number  x A  2  thickness  no. x  section i s  becomes =  Dividing  1 5e  cross  p e r gm o f s t o p p i n g  2  c ?i ev crrr £ m o i e c u 1e  z  (C D )n 2  t  stopping  i s deter-  6  ' x 6 . 0 2 5 x 1023  gm/cm  o f (C DL,)n 2  1 3  2  i s 45-5 yg/cm . 2  results  i n the required  -  99  -  APPENDIX B  ENERGY LOSS OF THE H E BEAM  IN A CARBON FILM  3  The energy ness  in yg/cm  section  To  loss  determine  is  2  e for  of  a 690 keV determined  3  H e beam  in a carbon  by c o n s i d e r i n g  film  of a given  the atomic  stopping  thickcross  He in carbon.  3  the  e for  3  e( He) 3  H e we u s e t h e  z  relation  from  (Nu 60)  e (proton)  2  E/3 where  z  For  from  2  (Nu 60)  carbon:  f o r an E = 690 keV  e ( He)  is  3.11  3  z x  = 3-H  2  e(proton) 230 keV  690 keV  from  (Wh 5 8 ) ,  =  3.11  x  37.32  Recalculate  ev  For  i n terms  e  - cm gm  carbon  21  this  of  ev  -  cm 9\  (  !ev  2  p e r gm o f  no.  - cm^ atom  of  loss  of  the  3  0  e  1 5  y atom  stopping  c  m  material  atoms  gm  A  e  10-15  10"  becomes  E  Multiplying  x  12 x  X  =  37.32  times  the  H e beam  ,  T2 X 10"  1 5  thickness  i n ev  X y  of  A = Avogadro's  number  2  carbon  in gm/cm  2  yields  the  energy  -  .". t h e carbon  energy film  loss  AE(keV) efl.. f o r :  J 103  =  a carbon  the- 3 He, .beam  AE i n keV o f ,a 6.90  thickness  AE(keV)  (yg/cm )  x  x  d  0  i.keV  3  H e beam as  10~  1 5  x 12  6.025  x  it  10  is  a function of passing  2 3  . c  M9 —"rt"  cm-  the  is:  To^  (yg/cm ) 2  thickness  1 . 8 8 ;x  -  through which  2  37.32  film  Ui  do  x  1.88  i,.s., n  100  10 =  of  10 y g / c m ,  1 8 . 8 ,keV..  2  the  energy  . j  loss  suffered  |,  ;  v  by  -  101  -  APPENDIX C  THE "EQUIVALENT FUNCTION  The a l p h a  yield,  target material  was  it  i s not c l e a r  to the He  i n t h e form  Consider  the formula  t  material 2  exists after thickness  t  [ o r an " e q u i v a l e n t  = aM  of  thickness.  Since exposure  calculated  o f d e u t e r i u m atoms i s g i v e n  thickness"  ^—  2  If the  concentration  (C Dt )n  3-3.1), t h e ( C D i ) n  concentration  polyethylene  then t h i s  a corresponding  (see s e c t i o n  from the observed "equivalent  (C^ijn,  is a  material  i n c i d e n t on t h e t a r g e t .  i n what form t h e t a r g e t  beam  3  barrier detector,  o f d e u t e r i u m atoms i n t h e t a r g e t  beam c h a r g e  d e u t e r i u m atoms would y i e l d  (COUNTS/yc)  by t h e S i s u r f a c e  measure o f t h e c o n c e n t r a t i o n 3  T H I C K N E S S " AS A  OF THE ALPHA Y I E L D  as r e c e i v e d  f o r a . g i v e n amount o f H e  POLYETHYLENE  a s an  (C D )n 2  i +  thickness"].  (A)  M where  AM  = total given  M  n o . o f **He p a r t i c l e s number o f i n c i d e n t  = no. o f He  particles  3  3  emitted  a  10"  i n c i d e n t on t h e t a r g e t  section  ( i n cm ) 2  H ( H e , p ) H e and i s d e t e r m i n e d 3  He  f o r the reaction by t h e e n e r g y o f t h e i n c i d e n t  l+  = concentration (in  3  1 9  = reaction cross 2  N  x  for a  He  c h a r g e Q, i n c o u l o m b s Of i n c i d e n t ; 1.6 x 10-19 = Q/1.6  at the target  o f t h e d e u t e r i u m atoms i n t h e t a r g e t  no. o f d e u t e r i u m  atoms/cm ) 2  material  -  The  ^He  detector  to 5.16  x  lb  subtends a g i v e n  of the  _ l 4  total  no. of He  Rearranging  =  5.16  in 3  He  (Ku The  particles  t a r g e t which  steradians.  produced a t the  i s equal  Hence  target  is  isotropic,  detector  H  have  1.6  x  D  10  x  (A)' we C  For an  o f 4ir  at the  _I  5.16  fl  s o l id angle  counts at the 5.16 x 10 »  4  =  -  s o l i d angle  assuming the number o f a l p h a  AM  102  x  IO"  10" *  x  1  1 9  x Q x a  (B)  energy of 690  i n c i d e n t He 3  the t a r g e t of 50 energy of 640  keV.  keV  and  The we  keV,  we  assume an average energy  reaction cross section a use  t h i s value of  a = 695  has mb  loss  a peak a t a = 695  x  10  _ 2 7  cm  2  55). concentration  ( C D i ) n as  ( i n g/cm ) of 2  N = P  2  +  (g/cm ) x 2  : = P x  R e a r r a n g i n g , we 32 x N 4 x A  Substituting  follows:  (no. of  (C Di )n/gm) x 2  4  x 4n  A n x  P =  N o f deuterium atoms i s r e l a t e d to the t h i c k n e s s P  ,  A  (no. of deuterium atoms per =  Avogadro's number  32 have  •  (B), we  have  P - f x H 8 6.025 x 6.02  x  1.6 10  5-16  23  IO"  1 5  x  Si Q  x  10  x - 4  10~  1 9  x 695  C  x  10"  27  D  Q  W  (C^DiJn)  -  Multiplying ethylene  t h e R.H.S. o f  t h i c k n e s s " Po in y g / c m  counts at the detector ije.  The  (C) by 1 0  Po(yg/cm ) 2  during  1 2  -  yields  3  =  10  =  6 . 0 2 x 10~  1 2  by  x 6.02 x 1 0 "  3  x  poly-  1 5  on t h e t a r g e t . (C /00)  x  D  Cn/Qo (number o f H e 4  i n t e g r a t i n g the He  q u a n t i t y o f y c and m e a s u r i n g  this integration.  the "equivalent  a s a f u n c t i o n o f t h e number o f ^He  per yc o f i n c i d e n t He  r a t i o CD/O.o i s o b t a i n e d  predecided  2  103  3  the t o t a l  counts/yc)  beam c u r r e n t  up t o a  number o f ^He  counts  -  10*1  -  APPENDIX D  "EQUIVALENT CARBON T H I C K N E S S " OF TARGET MATERIAL CALCULATED FROM THE  1  9  F RESONANCE SHIFT  As e x p l a i n e d  i n s e c t i o n 2.4.1, a c a l c i u m f l u o r i d e  behind  2  shift  t h e ( C D ( ) n " s a n d w i c h " t a r g e t a n d u s i n g a proton beam, t h e energy +  i n t h e 8 7 3 . 5 keV r e s o n a n c e o f t h e F ( p , a ) 1 g  This energy material. readily  shift  represents t h eenergy  T h i s energy  loss  As e x p l a i n e d  0 * r e a c t i o n was measured.  l o s s o f the protons i n t h e t a r g e t  t h i c k n e s s f o r a given target  stopping  i n 2 . 4 . 1 , due t o the l a r g e deuterium l o s s e s o f tine  " s a n d w i c h " t a r g e t s when e x p o s e d  t o the H e beam, i t was d e c i d e d t o a s s u m e 3  t a r g e t m a t e r i a l was composed c o m p l e t e l y o f carbon atoms f o r t h e s e  culations.  Consequently the energy  target material  loss suffered  i s c o n v e r t e d i n t o an " e q u i v a l e n t  " e q u i v a l e n t carbon t h i c k n e s s " f i l m which would  g i v e t h e same energy l o s s  target  cal-  by the p r o t o n s i n t h e carbon t h i c k n e s s " . 1  Thiis  i s then the t h i c k n e s s o f a c o m i p l e t e l l y c a r t o n  the  actual  The  a t o m i c s t o p p i n g cross section  (Wh  58) i n u n i t s o f e v - cm /atom.  ( f o r the p r o t o n foeaw iuise«0 a s  material.  s f o r protons i n carbon may b e ffowmdl iiirn  2  Recalculate  (  ev  I For  1 6  f o r t h e p r o t o n s o f a g i v e n energy can be  converted to a target  material.  the  t a r g e t was p l a c e d  e i n t e r m s o f e v - cm  9^  f  - crrr  ev  J  carbon t h i s  91  - ctrr atom  2  V A  per gm o f s t o p p i n g m a t e r i a l ! f no.  o f atoms) gm  becomes c  x  .» A « A v o g a d r o ' s  niuinfeeir  -  Dividing plying ness" E  the energy  by 1 0  5  105  -  l o s s A E ( e v ) o f t h e p r o t o n beam by e  ( t o change from g t o yg) y i e l d s  0  and m u l t i -  the "equivalent carbon  thick-  i n yg/cm 2  c  E  c  x 106  = e o ( e v - cm /gm) 2  AE  x  10  x 12  6  e x 6.025  The  atomic stopping  p r o t o n beam. 873  cross  10  x  section  The i n c i d e n t  keV r e s o n a n c e , c h a n g e s  yg/cm  2  2 3  e d e p e n d s on t h e i n c i d e n t e n e r g y o f t h e  e n e r g y o f t h e p r o t o n beam, r e q u i r e d with  the thickness of the target material.  f o r e t h e e v a l u e must be d e t e r m i n e d f o r e a c h c a s e  For example,  i f a p r o t o n beam o f e n e r g y 8 8 3 . 5  resonance", t h i s would  t h e z v a l u e f o r an i n c i d e n t  5.0  x 10~  1 5  .'. t h e " e q u i v a l e n t  carbon t h i c k n e s s " would 10 x  Ec  5.0 =  x  keV a c t u a t e d  10  10"  39.8  = kO y g / c m  2  3  1 5  loss  p r o t o n energy o f 883.5  e v - cm2 atom  x 12 x  10  x 6.025  x  be  6  10  2 3  There-  separately.  c o r r e s p o n d t o a 10 keV e n e r g y  and  to actuate the  t h e " 8 7 3 . 5 keV f o r the protons  keV i s  

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