Radiation level in the J-PARC Rapid Cycling Synchrotron after first study

J-PARC 3GeV RCSにおける初期ビーム試験後の残留放射線量

山本 風海   ; 林 直樹  ; 廣木 成治 ; 佐伯 理生二; 外山 毅*; 手島 昌己*; 佐藤 健一郎*

Yamamoto, Kazami; Hayashi, Naoki; Hiroki, Seiji; Saeki, Riuji; Toyama, Takeshi*; Teshima, Masaki*; Sato, Kenichiro*

The 3GeV RCS (Rapid-Cycling Synchrotron) in J-PARC has been commissioned in October of 2007. The most important issue in the beam study is to reduce unnecessary beam loss and to keep the beam line clean for the sake of maintenance and upgrade of the machines. In order to achieve this purpose, we observed the beam loss monitors located around the RCS beam line. We also investigated the residual dose of accelerator components during an interval of beam study. From these results, we found that beam loss points were the injection junction point, the branch of H0 dump and extraction line, transverse collimators, and dispersion maximum points in the arcs. Especially, the entrance of the primary collimator chamber was the most radio-activated points in the RCS. To make the best use of these results for beam commissioning, we managed to minimize the beam losses and succeeded in suppressing the residual dose to a level low enough to allows us to work close to those components.