Supported by the National Science Foundation and Indiana Universit

Foster, C.C.

Goodman, C.D.

Goulding, C.A.

Greenfield, M.B.

Rapaport, J.

Schery, S.D.

Ward, T.E.

Zafiratos, C.D.

English

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A STUDY OF THE Li(p,n) Be EXCITATION FUNCTION AT INTERMEDIATE ENERGIES USING RESIDUAL ACTIVITY 
T.E. Ward, C.A. Goulding, M.B. Greenfield,  C.C. Fos ter ,  and J. Rapaport 
Florida A&M University, Tal lahassee, Florida 3230 7 
C.D. Za f i r a tos ,  S.D. Schery, and C.D. Goodman 
Oak Ridge N a t i m l  Laboratory, Oak Ridge, Tennessee 37830 
The e x c i t a t i o n  funct ion  of t h e  7 ~ i ( p , n ) 7 ~ e  reac- r e s u l t  implies t h a t  (v: + 2.95 v;,) is independent of 
t i o n  was measured in  the  proton energy range of Ep= E, and t h a t  u(E) = 725.2869 (1/E) - 0.2952 With u i n  
60-200 MeV. Such a measurement was needed t o  determine mi l l i ba rns ,  E i n  MeV and a c o r r e l a t i o n  c o e f f i c i e n t  
t he  t o t a l  r eac t ion  c ros s  sec t ion  which i n  the  course of 
o ther  7 ~ i  s t u d i e s  could be used f o r  c a l i b r a t i o n  
purposes. 
The t o t a l  c ros s  sec t ions  were determined using 
standard o f f - l i ne  y-ray de tec t ion  techniques by 
measuring the  r e s idua l  7 ~ e  (53d) a c t i v i t y .  This method 
2 has been used a t  lower energies1 and a t  120 MeV t o  
c a l i b r a t e  l a r g e  volume neutron detec tors .  
Typically a t  each energy a 10-20 mg/cm2 enriched 
7 ~ i  t a r g e t  was i r r a d i a t e d  with 20-100 nA*hr of protons. 
After  bombardment the  i r r a d i a t e d  t a r g e t  was counted i n  
a prescribed counting geometry with known y-ray e f f i -  
ciency. The 7 ~ e  was i d e n t i f i e d  by its (10%) e l ec t ron  
capture  branch t o  the  477.4 keV l e v e l  i n  7 ~ i .  The 
samples were counted over s eve ra l  months t o  in su re  
t h e  477.4 keV y-ray decayed with the  7 ~ e  h a l f - l i f e  of 
53.3d. 
The r e s u l t s  of these  measurements a t  twelve 
energies  between 60-200 MeV a r e  shown i n  Fig. 1 along 
with the  previous r e s u l t s  of Schery, e t  a l .  ' The 
e r r o r  of our measurements was typ ica l ly  8-10%. A 
theo re t i ca l  ana lys i s  of t h e  s t r i k i n g  1 / ~  dependence 
has been made by Prof.  George Walker. Assuming the  
PWIA, an energy independent, very sho r t  range i n t e r -  
ac t ion  (using harmonic o s c i l l a t o r  wave funct ions  and 
neglec t ing  exchange e f f ec t s ) ,  y i e l d s  such a 1/E 
dependence f o r  t he  summed i n e l a s t i c  s c a t t e r i n g  d i f -  
f e r e n t i a l  c ros s  sec t ion  t o  a p a r t i c u l a r  s t a t e .  This 
1 )  S.D. Schery, L.E. Young, R.R. Doering, S.M. Austin, 
and R.K. Bhowmik, Nucl. I n s t .  and Meth. 147, 399 
(1977). 
2) C.A. Goulding, M.B. Greenfield,  D.E. Baincm, J. 
Rapaport, C.C. Fos ter ,  T.E. Ward, C.D. Za f i r a tos ,  
S.D. Schery, and C.D. Goodman, Nucl. Phys. A331, 
29 (1979) . 
Fig. 1 
A MSU (Ref. 1) 
# IUCF (Present Stwy) 
F i - w e  I .  Measurements of the ' ~ i  (p,n)7 ~ e  to ta l  cross 
section as a function of energy from t h i s  work (dots)  
and Ref. 1 ( tr iangles) .  The straight l ine represents 
a 1/E dependence. 


A Study of the 7-Li(p,n) 7-Be Excitation Function at Intermediate Energies Using Residual Activity

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A Study of the 7-Li(p,n) 7-Be Excitation Function at Intermediate Energies Using Residual Activity

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