Spatial Distribution Measurement of Neutrons Produced by 120-GeV Proton Beam in Concrete Shield

Abstract

"The shielding experiment was performed at the anti-proton (pbar) production target station in Fermi National Accelerator Laboratory to obtain benchmark data for various transport calculation codes. At the pbar target station, an antiproton production target, consisted of Inconel and copper disks, were irradiated by 120 GeV proton beam. The beam intensity was 2.3 x 10 12 proton per second. The iron and concrete shields were placed on the upper side of the target. The thickness of iron and concrete shields were 188 and 122 cm, respectively. Aluminum, bismuth, and indium samples were placed in the concrete shields to measure the neutron energy spectra in the concrete shields. After irradiation, induced activities in samples were measured by using HPGe detector. The reaction rate spatial distributions of 27 Al (n,Į) 24 Na, 209 Bi (n,xn) 203,204,205,206 Bi, and 115 In (n,n') 115m In reactions were measured in the concrete shields. The neutron energy spectra in the concrete shields were also obtained by unfolding the measured reaction rates with the aid of neutron induced reaction cross sections.

Measurements of the neutron activation cross sections for Bi and Co at 386 MeV

“…In lieu of measurements, neutron-activation cross sections are evaluated on the assumption that neutroninduced cross sections above 100 MeV are approximately equal to proton-induced cross sections of the same energy or by theoretical model calculation. The cross section data of 209 Bi(n, xn) and 59 Co(n, xn) reactions, in particular, were reported for energies up to 150 MeV (1,2) , and these have been applied to high energy neutron spectrometry (6)(7)(8) . But calculation of the neutron-induced activation above 150 MeV is problematic due to absence of experimental data.…”