JX-11

NEUTRON PRODUCTION BY HEAVY ION INTERACTION
FOR NUMATRON SHIELDING DESIGN
Takashi Nakamura
Institute for Nuclear Study, University of Tokyo
For shielding design of the high energy heavy ion accelerator,
NUMATRON, it is indispensable to get the information on the neuThe measured totaltron production by heavy ion interaction.
neutron yields for proton, deuteron and alpha particle reactions
have summarized for a variety of target materials in ref. l andtheir results are shown in fig. l. Figure l shows that the neutron yield from proton reactions increases with the proton energy
and the target atomic mass, while the increase of the yield withthe target atomic mass is much less apparent for deuteron andalpha particle reactions. Ref. l also includes the neutron production by l2c-, l4N-, 20Ne-ion bombardment of energy 10.4 MeV/u
as shown in fig. 2. These results indicate the following facts:i) The neutron yield increases with the target atomic mass,
but is practically constant for targets from Cu to Pb.
ii) The yield increases with increasing the ion energy, butdoes not increase with increasing the ion atomic mass, forthe same energy per nucleon of the ion.
For higher energy region, Santoro2) has calculated the neutron energy spectrum d2~/dEdil from Fe bombarded by 900-MeV l2cion (75 MeV/u) and Gabriel et al.3) from C bombarded by 1.2 GeV
l2c ion (100 MeV/u). The total neutron yield for a thin target,~y is obtained fromL! y ==s·r

cm2/g per incident ion, ( l)

h"TL
3530

Thtt

c: 25.Q'c 20ef-;~ !5..

Q 10!.
0Cu~I0'"'
AgTa;I fu'"'

PbAItC<tlc0 ______.J._ _ ______L _100500__l _ _ _o~--~150200250:, of target nucleus
Incident particle energy (MeV)
Fig . .f..

Plot of •uurron yields v.-: inciderlt particle er1ergy [or severalcoml:inalions of tarrcts atJd ions. · (I} Smith and Kruga, M nS04,(:..'; ]Ci. Mi!!bum,-Kap/an, und Mo.~·er, Mn SO.J, (3) Allen, Necha/,
Sltli, and Jeunings, 32stn,p)32p, (4! Crandell. Mil: bum, Jnd Schechter,.Mn so 4 , (5) Wadm,~n (~0 and 80-Ji1eV a++ un Ta), 58Ni(n,p;58co,Fig. 2Neu!ron ydds {,·om thi~P-targct hornbardments byhemy ions of approxirnc:tdy ! 0 !1c V per nucleon. The
12C,Qfor!4-l-/0cV14N'1 andare a
fur 201-MeVrej.J){6) Wadman (23.2- ro 40.R-MeVa on C). J..toderoted BF3 curve:J5-Jwpe accurate; yield value pMbabfy high. (From Yej.

f203

where No= Avogaa~o's number
A = target atomic mass.
......
"'The values of 6Y calculatedN:£ufrom eq.(l) are shown as az'
function of ion energy in fig.
03.
The value of ~Y for 101-uw
MeV/u energy was estimated by(/)
dividing the neutron yield forthick targets in fig. 2 into
one range thickness.
Then thetotal neutron yield for a thick ~target, Y is given bySY

J:Y

dtn/p

(2)

r:C ION
0.1

irange of bombarding
ion in g/cm2.

where RCu100
10
For the case of 900-MeV
ION ENERGY, MeVIAMU
l2c on Fe, the yield Y is
0.23 and for 1.2 GeV l2c
A~oughesti~ationof the tOtal neutron yieldf;~.J.
on C, Y is 0.39 from eq.(2).
for thin target by 12 c ioA' bomba~dmeGe
The NUMATRON intends to havethe highest final ene+gy of
1.47 GeV/u for l2c, l4N and 20Ne ion beams among of heavy ions.
Since there is no data on neutron production due to 1.47 GeV/uheavy ion interaction, it must be estimated from the data due toproton reaction.
The estimated neutron yields are as follows;
TargetCuu1.47-GeV/u protonl. 4 7- GeV /u l 2 c

11.4"-'40Referencesl) H.W. Patterson and R. H. Thomas, Accelerator Health Physics,Academic Press, 1973, p. 128 - 148.
2) Cited in A. Rindi, LBL-4212 (1975).
3) T. A. Gabriel et al., ORNL-TM-4334 (1973).

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