This work was supported by the National Science Foundation Grant NSF PHY 81-14339 and by Indiana Universit

Kwiatkowski, K.

Viola, V.E. Jr.

Walker, M.

Ward, T.E.

English

IUScholarWorks

SEARCH FOR FISSION-LIKE PROCESSES I N  THE 200-MeV p+ 2 8 ~ i  REACTION 
M. Walker, K. Kwiatkowski, T.E. Ward, and V.E. Viola, Jr. 
Indiana Univers i ty  Cyclotron F a c i l i t y ,  Bloomington, Indiana 47405 
S tud ies  of t he  200-MeV p + 2 8 ~ i  reac t ion  a t  
backward angles  show evidence of s i g n i f i c a n t  amounts 
of r e l a t i v e l y  e n e r g e t i c  ions  of Z > 9. I n  order  t o  
examine the  p o s s i b i l i t y  t h a t  these  y i e l d s  may be the  
r e s u l t  of a two-body breakup (f i s s i o n - l i k e )  process ,  a 
coincidence experiment was performed. 
A 100 pg/cm2 i so top ica l ly - sepa ra t ed  t a r g e t  of 2 8 ~ i  
was bombarded wi th  200-MeV protons from the  Indiana 
Un ive r s i ty  Cyclotron F a c i l i t y .  The fragments were 
de tec t ed  wi th  a p a i r  of gas-ionization-AE and 
semiconductor-E d e t e c t o r  te lescopes  ope ra t ing  a t  gas 
p res su res  of 6 and 9 t o r r  of isobutane. Windows on the  
gas  i o n i z a t i o n  d e t e c t o r s  were 70 pg/cm2 polypropylene. 
Figure  1. Charge i d e n t i f i c a t i o n  spectrum AE versus  E 
Fragments with atomic numbers up t o  2112 wi th  ene rg ie s  contours of fragments from p+28~i a t  200 MeV f o r  11' 
and 9 t o r r .  Z=6 is ind ica t ed  by arrow. 
a s  low as  -0.2 MeV/nucleon could be de tec t ed  wi th  t h i s  
system. One d e t e c t o r  te lescope served a s  a de f in ing  
d e t e c t o r  (A8=+2 degrees)  and was kept f ixed  a t  forward 
l abora to ry  angles  (11, 30, and 55 deg.) while t h e  
second d e t e c t o r  ( b e e 4  degrees)  was r o t a t e d  through 
c o r r e l a t i o n  angles ,  ~ A B ,  from approximately 40 t o  180 
degrees i n  the  l abora to ry  system. Both s i n g l e s  and 
coincidence d a t a  were recorded on l i n e .  
I n  Fig. 1 is shown an example of d a t a  taken a t  11 
by the  de f in ing  de tec to r .  I n  t h i s  AE versus  E contour 
taken a t  a gas pressure  of -9 t o r r ,  Z values  of up t o  
2112 a r e  c l e a r l y  defined. Because of t h e i r  low energy 
l o s s  i n  the  gas- ionizat ion d e t e c t o r ,  Z=l and Z=2 a r e  
no t  c l e a r l y  def ined i n  these  spec t r a .  I n  Fig. 2, taken 
a t  170' and 9 t o r r ,  fragments with charges up t o  Z=9 
a r e  c l e a r l y  observed, i n d i c a t i n g  t h a t  some heavy 
fragments a r e  being emit ted  i n  the  backward d i r ec t ion .  
However, t he  coincidence s p e c t r a  i n d i c a t e  few heavy 
fragment-heavy fragment coincidences.  In s t ead  the  
Figure 2. Charge i d e n t i f i c a t i o n  spectrum AE versus  E 
contours  of fragments from p + 2 8 ~ i  a t  200 MeV f o r  170" 
and 9 t o r r .  Z=6 is ind ica t ed .  
heavy fragments a r e  found t o  be p r imar i ly  i n  
coincidence wi th  H o r  He. Fur ther  work and a n a l y s i s  
a r e  i n  progress  i n  o rde r  t o  understand the  y i e l d s  and 
sources  of t hese  e n e r g e t i c  fragments emit ted  a t  
backwards angles.  


Search for Fission-Like Processes in the 200 MeV p+ 28-Si Reaction

https://scholarworks.iu.edu/dspace/bitstream/2022/2733/1/iucf_1982_151.pdf

Search for Fission-Like Processes in the 200 MeV p+ 28-Si Reaction

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