Challenge to charge exchange with pure carbon foil in the J-PARC 3GeV synchrotron

Nakanoya, Takamitsu  ; Yoshimoto, Masahiro  ; Saha, P. K.   ; Takeda, Osamu*; Saeki, Riuji*; Muto, Masayoshi*

In the J-PARC 3GeV Rapid Cycling Synchrotron (RCS), the 400MeV H beam is changed to H+ beam by a charge exchange foil and accelerated to 3GeV. So far, RCS had used two types of charge exchange foil. One is the HBC (Hybrid Boron mixed Carbon) foil and the other is the Kaneka GTF (Graphene Thin Film). HBC foil is a patented deposition method developed at KEK for the stable production of thick carbon foil. Initially, the RCS used HBC foil produced atKEK. However, in 2017, JAEA had started HBC foil production and has been using it since then. Recently, we have succeeded in depositing thick pure carbon foil, which had been considered difficult to produce by the arc deposition method. As a new challenge, this pure carbon foil was used in the user operation from March 2023. As a result, Pure carbon foils showed less deformation and more stable charge exchange performance than HBC and GTF.