Progress status in fabrication of HBC stripper foil for 3-GeV RCS at J-PARC in Tokai site

In the 3-GeV Rapid Cycling Synchrotron (RCS) at Japan Proton Accelerator Research Complex (J-PARC), we adopted thick Hybrid type Boron-doped Carbon (HBC) stripper foil for multi-turn H- charge-exchange injection. The HBC stripper foil developed at KEK has demonstrably improved the foil lifetime significantly. In addition, Graphite Thin Films (GTF) developed by KANEKA corp. was attempted to use for user operation. The GTF is a multilayer graphene sheet and it is expected to be a new candidate for highly durable charge stripping foil. HBC and GTF foils can be both employed the J-PARC RCS for long-term user operation. Early manufacturing of the stripper foil for the J-PARC was carried out according to the following two steps: foil fabrication at the KEK Tsukuba site and foil preparation at the JAEA Tokai site. Recently, the HBC foil deposition apparatus was relocated from KEK to JAEA, and new HBC foils were fabricated at the Tokai site. The performance of the new HBC foil was verified to be equivalent to the original HBC foil with offline beam irradiation tests. Furthermore, the use of the new HBC foils was successfully demonstrated during RCS user beam operation for one week.

Measurement of radioactivity and evaluation of activated nuclides due to secondary particles produced in stripper foil in J-PARC RCS

Multi-turn charge-exchange beam injection is the key technique to achieve high-intensity proton beam accelerators. In J-PARC RCS, 400-MeV H- beams from LINAC are injected into stripper foils such that most of the beams are converted into protons. The stripper foils are irradiated not only with the injected H- beams but also with the protons circulating during the beam injection period. The high energy and intense beam irradiation into the foil generates secondary neutrons and protons via nuclear reactions. These secondary particles cause high residual activation around the stripper foils. Therefore, an activation analysis method that uses sample pieces is required to investigate the secondary particle. Furthermore, a new experimental system to measure secondary particles from the foil was installed at the L3BT 100BD line. Initial testing of the system has been completed, and beam testing will commence in October 2018.