Vacuum system of the 3 GeV-RCS in J-PARC

J-PARC 3GeVシンクロトンの真空システム

荻原 徳男; 金正 倫計  ; 神谷 潤一郎   ; 山本 風海   ; 菅沼 和明 ; 吉本 政弘  ; 齊藤 芳男*

Ogiwara, Norio; Kinsho, Michikazu; Kamiya, Junichiro; Yamamoto, Kazami; Suganuma, Kazuaki; Yoshimoto, Masahiro; Saito, Yoshio*

The 3 GeV-RCS in J-PARC project accelerates a proton beam up to 3GeV. The cumulative energy dose will be of the order of 100 MGy for 30 years of operation. So as to minimize the radiation exposure during maintenance, it is necessary to compose the vacuum system with reliable components which have long life time in such a high level of radiation. In addition, it is necessary to keep the operating pressure with beam in ultra high vacuum for suppressing the pressure instability. The ring is divided by the isolation valves into 6 sections, which can be pumped down independently. For avoiding any eddy current loss ceramic ducts are used in the magnets. These ducts are connected to the Ti ducts, putting the Ti bellows between. Here, we adopt pure Ti as a material for the ducts and bellows because of its small residual radioactivity. The ring is evacuated with 20 ion pumps (0.7 m/s) and 20 turbomolecular pumps (TMPs) (1 m/s), which are attached to the Ti ducts. The TMPs are used for not only rough pumping but also evacuation during the beam operation. We have already succeeded in developing some components such as large aperture ceramic ducts and TMPs with high radioactive-resistance, as well as several kinds of heat treatment to reduce the outgassing. Now we have almost installed the vacuum system.