Improvements of the charge exchange system at the 3GeV RCS in J-PARC

J-PARC 3GeV RCSにおける荷電変換装置の改良

吉本 政弘  ; 竹田 修; 川瀬 雅人; 山崎 良雄 ; 金正 倫計  ; 斉藤 義男*; 壁谷 善三郎*

Yoshimoto, Masahiro; Takeda, Osamu; Kawase, Masato; Yamazaki, Yoshio; Kinsho, Michikazu; Saito, Yoshio*; Kabeya, Zenzaburo*

J-PARC 3GeVシンクロトロン(RCS)では、フォイルを用いたHの荷電変換方式を採用している。そのため荷電変換装置は遠隔自動フォイル交換機能付きを含む3つのフォイルを駆動する装置から成り立つ。RCSのビームコミッショニングの開始直前であった2007年の夏にこの荷電変換装置に駆動部のトランスファーロッドに用いる磁気結合部が外れゲートバルブに挟まって壊れるという、重大な問題が生じた。われわれはこの問題の原因を追究し、材料選定を含む構造設計からやり直し、試験片を用いた耐久試験を行った。その結果をうけて、2008年に改良した荷電変換装置を再設置した。

At the 3 GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex), the scheme of H charge exchange injection using stripping foils is adopted. The charge exchange system is composed of three stripping foil devices. The first stripping foil device, which converts the H beam from the 181 MeV LINAC into the H beam, can replace the broken foil with new one in vacuum remotely and automatically. In September 2007, mechanical trouble with the first stripping foil device had occurred just before the RCS beam commissioning was started. The magnetic coupling of the transfer rod had been decoupled and the transfer rod had been broken which was caught in the vacuum gate valve. We studied the trouble cause, re-examined the structural design and the selection for the material, and then verified the specification from endurance tests with sample pieces. Then the improved device was installed in the ring in September 2008.