Measurement of activation cross sections of the target and the proton beam window materials at J-PARC

Abstract

To improve the accuracy of the nuclear design for spallation neutron sources and transmutation systems, nuclear reaction cross sections are required. Considering decommissioning of the accelerator facilities, accurate cross sections are mandatory. The activation cross sections have been measured in several facilities. However, they have low accuracy and precision. Especially, since there is almost no data for 3 GeV protons which are used for the spallation neutron source (MLF) in J-PARC, the experimental data is required for in order to improve the target materials. For the sake of the forthcoming full-time measurement of the activation cross sections for various nuclei, we measured the cross sections of aluminium with 0.4 GeV, 1.3 GeV, 2.2 GeV, and 3.0 GeV protons as a test case. It was found that more accurate data than current ones would be measured by using precise beam controls and highly accurate beam monitoring. We compared the experimental data, the evaluated data (JENDLHE/2007), and the calculations with several intranuclear cascade models using the PHITS code. Although the experimental data agreed with JENDL-HE/2007, the calculations underestimated by about 40%. This arises from the evaporation model (GEM) being included in PHITS code. We found that the calculations could be made to agree with the experimental data by upgrading the PHITS code.