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CO:PARISON OF BEASURED NEUTRON AID PROTON SPECTRA WITH CALCULATED
SPECTRA IN THE ENERGY REGION BET:EEN. SO AND 160 MeV*
W. A. Gibson, W. R. Burrus, W. E. Kinney, and J. W. Wachter
Oak Ridge National Laboratory, Oak Ridge, Tennessee
mn 2
1965 F. Johnson, General Dynamics Corporation, Fort Worth, Texas
NIE
A principal objective of the experimental program at ORITI to measure the
seconda z'y proton and neutron spectra from targets bombarded by high-enercy protons
is to generate data to compare with the theoretical Monte Carlo calculations of
Bertini? and Kinney. ?
The enercy spectra of secondary protons and neutrons emerging from targets
bombarded by a collimated beam of 160-MeV protons were obtained with a proton
recoil spectrometer, covering the energy range between 50 and 160 MeV.
The following two types of comparisons for secondary neutron production are
presented for the energy region between 50 and 160 MeV:
Cross Sections - Since the targets used in making these reasurements were thin,
the incident proton beam lost less than 10% of its energy in traversing the target.
Furthermore, the probability of secondaries produced undergoing additional nuclear
interactions was small. Comparisons of proton production will also be made for this
case.
Transport - In this case, targets wilich completely stopped the incident
protons were considered.
Two factors must be considered in making direct ccraparisons between the cal-
culations and the measurements: The resolution of the spectrometer causes mixing
*Research sponsored by the National Aeronautics and Space Administration (NASA Order
R-104) under Union Carbide Corporation's Contract with the U. S. Atomic Energy
Commission.
'I'
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2
of adjacent regions of the spectrum, an effect which is especially significant
in cases where the energy spectrum chances rapidly such as in the case of proton
cross sections; the calculational model must correctly simulate the experimental
conditions. (maus angular data calculated without regard to the point of inter-
action are not comparable since for thick-target measurements a particle emitted
at a given angle in the target riay pass through the spectrometer, whereas a particle
emitted at the serie angle tut at a point farther from the spectrometer may not enter
the spectrometer.)
The resolution effect was included by smearing the calculated spectrum with
& Gaussian resolution function which closely approximates the resolution function
of the experimental results analyzed by the SLOP code. The correct computational
model was obtained by writing a ilonte Carlo analysis code to consider only those
particles which correspond to particles entering the spectrometer under actual
experimental conditions. Figures 1 and 2 are cross-section comparisons for protons
and neutrons at 60 and 15°, respectively, and Figs. 3 and 4 show the yield spectra
for neutrons from thick targets. The shaded band in the figures is the 68% confi-
cence interval for the experimental data analyzed by the SLOP code. The errors on
the calculated data of Pertini and Kinney are also the 68% confidence limits. In
both cases the errors represent the statistical error only. Comparisons with addi-
tional targets and configurations are continuing.
The theoretical and experimental cross sections, in general, agree favorably.
In most cases the differential cross sections at 45 and 60° integrated with respect
to energy from 50 to 150 MeV agree within expected error, and in a few cases agree-
ment withi.. expected crror over the entire energy range above 50 MeV is found. In
order to find improved fits, the calculations were done with three different potential
-LEGAL NOTICE -
TNreport no prepared as u kroat of Covenant sponsored work. Molther the United
duales, nor Une Coanisolon, nor uay pero kung on batail of the Counoslan:
A Mue, uy warranty or reprenatation, expressed or inalind, nu respect to the army.
ry, coupinho, or nehme of the laboruuon could u W, roron, or that the ma.
of any taformation, appunto, wound, or proces. .xlound in de moont may not inte
printly omad mahu: or
. An e. Wy liabiliser nu roopact to the we of, or for anapoo roselling from
mol way W usthou, mann, method, or pror... dxcloud In wiropuri.
As und in the above, pornoa ating on bowall of the Coanis.100" incinde uy a.
dlose or rouincwr of e Condicion, or oplore of much contractor, to the ormt ut
w doployee or conenklor of the Cowalsson, or enplegue of such contractor prepare,
di numatou, or proridro ketuo to, uy thiorulou pur to Nonploss of or robinet
ju the Counseloa, or ha employby mu suck cool actor.

well shepos, with those presented here judced as the ones giving the best overall
agreement with c::periment.
T::e disagreement between the experimental results and the transport-code
calculations seems to be more serious; in all cases the calculation predicts yields
which are too lazce. Little possibility exists for changes in this code since the
only variablc parameters occur in the input data obtained from the cross-section
code. Such ezrects as Coulomb scattering of the incident protons have been included,
and other factors are being investigated which might improve comparisons with
experiments.
References:
1. 11. W. Bertina, i onte Carlo Calculations on Intranuclear Cascades, ORNL-3383
(lipril 23, 1963).
2. W. E.Kinney, The dueleon Inansport Code, TS, ORNL-3510 (August 1934).
3. W... Gibson, !. R. Burrus, J. W. Waci:ter, and C. F. Johnson, Neutron Physics
Division Annual Progress Report for Period inding Aurust 11963, ORNL-3499,
Vol. II, p. 109.
4. J. ll. Bachter, 1. A. Ginson, W. R. Burrus, and C. F. Johnson, Neutron Physics
Division al Progress Report Tor Period Ending August 1, 1963, ORNL-3499,
Vol. II, p. 89.
V. D. Bocert and W. R. Burrus, Heutror. sics Division Annual Progress Report
for Period Ending September 1, 1952, ORNI-3360, p. 22.
5.
Fis. l.
Secondary Production Cross Section at 60° for 160-Me V
Proto: Incident on a 0.5419-g/cm'-Thick Al target. (Note:
e c.perimental data labeled "T.O.F." are time-of-flight
results discussed in a paper by R. W. Pee.lle et al., these
procochins.)
Fig. 2. Secc..dary neutron Produccion Cross Section at 15° for 160-MOV
Procons Incident on a 3.224-3/cma-Thick Co target.
rig. 3.
Secondary ietron Yield from a 26.89-g/cm²-Thick Al Target
at 10 end 45° to the Incident lóo-MeV Proton Beam. The
incident beam was completely stopped in the target.
Fig. 4.
Secondary weutror. Yield from a 44.33-g/cma-Thick Bi Target
at 10 and 45° to the Incident 160-lue V Proton Beam. The
incident beam was completely stopped in the target.
UNCLASSIFIED
ORNL-DWG 64-8624 R4
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Secondary Proton Cross Section at 60° for 160-MeV Protons
Incident on 0.549 g/cm2 Aluminum Target.
UNCLASSIFIED
ORNL-DWG 64-9104R

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NEUTRON CROSS SECTION ( millibarns/steroviai: ve!)
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Secondary Neutron Cross Section at 45° for 160 - MeV
Protons Incident on 3.224 g/cm? Cobalt Target.
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ORNL-DWG 64-8623

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Neutron Yield for :30-MeV Protons Incident on 26.89 g/cm2
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UNCLASSIFIED
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Neutron Yield for 160-MeV Protons Incident on
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197
DATE FILMED
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LEGAL NOTICE

This report was prepared as an account of Government sponsored work. Neither the United
States, nor the Commission, nor any person acting on behalf of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect to the accu-
racy, completeness, or usefulness of the !nformation contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this report may not infringe
privately owned rights; or
8. Assumes any liabilities with respect to the use of, or for damages resulting from the
use of any information, apparatus, method, or process disclosed in this report.
As used in the above, "person acting on behalf of the Commission" includes any em-
ployee or contractor of the Commission, or employee of such contractor, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to, any information pursuant to his employment or contract
with the Commission, or his employment with such contractor.
KRA-
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