Evaluation of activated nuclides due to secondary particles produced in stripper foil in J-PARC RCS

Yoshimoto, Masahiro  ; Saha, P. K.   ; Kato, Shinichi; Okabe, Kota  ; Yamamoto, Kazami   ; Kinsho, Michikazu  

The charge exchange multi-turn beam injection scheme is adopted in the J-PARC 3GeV Rapid Cycling Synchrotron Accelerator (RCS) due to achieve 1MW beam power operation. In the conventional multi-turn beam injection scheme, which is provided by only the septum and bump magnets, injecting turn numbers are limited by the beam losses at the septum. On the other hand, charge exchange multi-turn beam injection does not cause the beam losses at the septum; there is no restriction in principle on the injecting turn number. However, high residual doses are observed around the stripper foil. During the charge exchange multi-turn beam injection, not only the injecting beam but also circulating beam hit the foil, and then a large number of secondary particles, namely protons and neutrons, are generated. PHITS simulation results indicate that the secondary particles cause the high residual doses around the foil. To verify this examination, secondary particles measurement is key issue. Then, a new independent type foil introducing device is installed in the 100-deg dump beam transport line in order to construct a simple experimental system for secondary particle measurements. We plan the two experiments by using this system; one is a directly secondary particle detecting method, and the other is a radioactivation analysis method with metal sample pieces. Now, we started the study of how the identification of species and energies of the secondary particles with PHITS code. Irradiation target of Cu is adopted and irradiated proton or neutron beam with various energy range. Then radio-nuclides emitted the -ray are picked up. Moreover, the radio-nuclides, whose reaction efficiencies due to beam species or energy are different, are searched for the indicator of the secondary particles. From the simulation results, Zn is extremely suitable for a proton beam indicator, and Co and Co are also suited for a neutron and proton indicator respectively.