Shielding Experiments Under JASMIN Collaboration at Fermilab(III) - Measurement of High-Energy Neutrons Penetrating a Thick Iron Shield from the Antiproton Production Target by AU Activation Method

In an antiproton production (Pbar) target station of the Fermi National Accelerator Laboratory (FNAL), the secondary particles produced by bombarding a target with 120-GeV protons are shielded by a thick iron shield. In order to obtain experimental data on high-energy neutron transport at more than 100-GeV-proton accelerator facilities, we indirectly measured more than 100-MeV neutrons at the outside of the iron shield at an angle of 50° in the Pbar target station. The measurement was performed by using the Au activation method coupled with a low-background γ-ray counting system. As an indicator for the neutron flux, we determined the production rates of 8 spallation nuclides ( 196 Au, 188 Pt, 189 Ir, 185 Os, 175 Hf, 173 Lu, 171 Lu, and 169 Yb) in the Au activation detector. The measured production rates were compared with the theoretical production rates calculated using PHITS. We proved that the Au activation method can serve as a powerful tool for indirect measurements of more than100-MeV neutrons that play a vital role in neutron transport. These results will be important for clarifying the problems in theoretical calculations of high-energy neutron transport. Work supported by a Grant-in-Aid from the Ministry of Education (KAKENHI 19360432 and 20354764), Japan and by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. Published in Journal of the Korean Physical Society. Corresponding author. E-mail : hiroshi.matsumura@kek.jp