This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Bent, R.D.

Berg, G.P.A.

Brown, J.D.

Dillig, M.

Emery, G.T.

Foster, C.C.

Hardie, G.

Homolka, J.

Jacobsen, E.R.

Kienle, P.

Nann, H.

Pollock, R.E.

Rehm, K.E.

Schott, W.

Segel, R.E.

Singh, P.P.

Tung, T-Y.

Yu, Z.

English

IUScholarWorks

REPORT ON EXPERIMENT CE06: 
MEASUREMENTS OF NUCLEAR REACTIONS USING RECOIL DETECTION 
R.E. Senel, T-Y. Tung, and 2. Yu 
Northwestern University, Evanston, Illinois 60201 
J. Homolka and W. Schott 
Technische Universitat Miinchen, 0-8046 Garching bei MGnchen, Germany 
R. D. Bent, G.P.A. Berg, C.C. Foster H. Nann, R.E. Pollock, and P.P. Singh 
Indiana Universit y Cyclotron Facility, Bloomington, Indiana 4 74 05 
G. Hardie 
Western  Michigan University, Kalamazoo, Michigan 49008-51 51 
K.E. Rehm 
Argonne National Laboratory, Argonne, Illinoia 60439 
J.D. Brown and E.R. Jacobsen 
Princeton University, Princeton, New Jersey 08540 
G.T. Emery 
Bowdoin College, Brunswick, Maine 04011 
M. Dillig 
University of Erlangen-Niirenberg, Erlangen, Germany 
P. Icienle 
Gesellschaft fiir Schwerionenforschung, Darmatadt, Germany 
1. 12C(~,12N)n,  l3C(p7l3N)n, 12C(p,12 c ) ~ ,  and 13C(p ,13~)p  at 200 MeV 
This experiment was run at the cyclotron in November, 1988 and a.nalysis of the data 
is nearly complete. The purpose of the experiment was to study these reactions when the 
nucleons are emitted near 180°. A study1 of the elastic scattering of protons by 12C had 
reported cross sections at backward angles that were much larger than those predicted 
by the optical model. At 157' (cm), the largest angle at which data were ta,ken, the 
differential cross section was found to be 17.5 nb/sr and rising with increasing angle. The 
present experiment was undertaken not only to extend the 12C(p,p) measurements out to 
180°, but also to broaden the scope of the investigation to a systematic study of (p,n) 
reactions near 180". To this end, differential cross sections were also measured for the 
l3 C(p,p), l2 C(p,n), and l3 C(p,n) reactions. Measurements at nucleon emission angles at 
or near 180' were made possible by detecting the accompanying C or N recoils. 
The experimental arrangement was very similar to that used in previous recoil detec- 
tion experiments done at IUCF2. Foils of l2 C and l3 C, approxima.tely ZOO pg/cm2 thick, 
were bombarded with 200 MeV protons and the recoil ions were magnetically analyzed by 
the QQSP spectrometer. The detector stack at the output of the spectrometer consisted 
of a pair of position sensitive parallel plane avalanche counters, separated by a 12 cm drift 
space, and a proportional counter. The QQSP was set to cover the angular range from 
-10" to +zO. 
The (p,p) and (p,n) differential cross sections are shown in Figs. 1 and 2, respectively. 
The present results combined with those of Meyer et  al.' lead to the conclusion that the 
12C(p,p) cross section peaks around 160". The 13C(p,p) cross section also falls towards 
180° with about the same slope, but is smaller by about a factor of 2.5. The (p,n) cross 
sections are much smaller and, within the limited statistics, show no obvious trend with 
angle. The 13C(p,n) cross section is the larger of the two by a factor of 2-3, perhaps 
reflecting the loosely bound neutron. 
12 13 C(p,p) and C(p,p) T n = 200 MeV 
165 170 175 180 
PROTON CM ANGLE (degrees) 
Figure 1. Differential cross sections for the '2C(p,12C)p and the 13C(p,13C)p reactions at 
Tp = 200 MeV. Both the cross sections and the angle are in the center-of-mass system, 
and the angle is that of the emitted proton relative to the incident beam. 
11. Recoil Detection at the Cooler 
It has long been recognized3 that a, storage ring with extremely thin internal taxgets 
offers the ideal environment for performing recoil detection experiments. Experiment CEO6 
has been approved for studying the 1 2 C ( p , ~ )  and (p,y) reactions, and a facility is being 
installed in the T region of the Cooler ring for this and other future recoil experiments. 
The 6" magnet that is being placed in this region will be used to bend the recoils away from 
the beam, magnetically analyze them, and send them through a detector stack. Extensive 
12 13 C(p,n) and ~ ( p , n )  T - = 200 MeV 
NEUTRON CM ANGLE (degrees) 
Figure 2. Differential cross sections for the 12C(p,12N)n and l3 C(p,13N)n reactions. 
Figure 9. Diagram of the recoil detection system to be illstalled in the T region of the 
Cooler ring. 
orbit calculations have been performed, and on the basis of these a detector system and its 
housing have been designed. There will be a parallel plate avalanche counter with position 
wires in both the bend and the non-bend plane, a proportional counter, and an array of 
silicon microstrip detectors. A diagram of the system is shown in Fig. 3. At the present 
time, the avalanche counter has been designed and an order has been placed for the silicon. 
It is expected that the entire system will be assembled and tested by the end of calendar 
year 1990. 
1. H.O. Meyer, P. Schwandt, W.W. Jacobs, and J.R. Hall, Phys. Rev. C 27, 459 (1983). 
2. J. Homolka, W. Schott, W. Wagner, W. Wilhelm, R.D. Bent, M. Fatyga, R.E. Pollock, 
M. Saber, R.E. Segel, P. Kienle, and K.E. Rehm, Nucl. Inst. Meth. A260,418 (1987). 
3. Indiana University Cyclotron Group, The IUCF Cooler- Tripler Propo~al  to the NSF, 
Indiana University (1980). 
PIONIC ATOMS AS COMPOUND STATES IN NUCLEON-NUCLEUS COLLISIONS: 
STATUS REPORT ON THE COOLER EXPERIMENT CEO2 
H.O. Meyer, L. Bland, G. Emery, M.G. Minty, H. Nann, P.V. Pancella, S. Pate, 
R. Pollock, B.v. Przewoski, T. Rinckel, P. Schwandt, and F. Sperisen 
Indiana Univer~i ty  Cyclotron Facility, Bloomington, Indiana 4 7405 
1. Introduction 
The formation of pionic atoms in nuclear collisions just below the T-  production 
threshold has been postulated some time ago.' Attempts to observe this process have so 
far not met with success. The goal of experiment CEO2 is to measure a cross section 
excitakion function for p+13C elastic scattering, and to look for a resonance near the n- 
production threshold. 
An update of the original proposal of 1984 was presented during PAC XXIX in De- 
cember, 1989. In the light of our present understanding of the Cooler performance, the 
experiment still seems to be feasible, although the demands on energy resolution and lumi- 
nosity are substantial. It was concluded that in order to find and map out the resonance 
(corresponding to a pionic 140 in the Is state) with 4 keV energy resolution, 25 shifts of 
beam time should be sufficient. This does not include beam time for the development of 
the appropriate experiment a1 conditions. 
The apparatus for the detection of the scattered protons will be taken over from 
the CEOl experiment (see elsewhere in this annual report). Since backward angles are 
of interest, the CEOl detector arrangement will be reversed. In addition, in order to 
more clearly define the experimental signature, a detector for the recoiling target nuclei 
will be mounted in the forward direction. Tests with heavy ion beams from the Notre 


Report on Experiment CE06: Measurements of Nuclear Reactions using Recoil Detection

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