Turbomolecular pump for achieving ultra-high vacuum in a high-power proton accelerator vacuum system

Kamiya, Junichiro   ; Kinsho, Michikazu  ; Ogiwara, Norio*; Sakurai, Mitsuru*; Mabuchi, Takuya*; Wada, Kaoru*

Challenges for ultrahigh vacuum (UHV) region in J-PARC 3 GeV rapid cycling synchrotron (RCS) come from the large static and dynamic outgassing. In the RCS vacuum system, turbomolecular pumps (TMP) have been used as main pump because it can evacuate such continuous and additional outgassing with a large pumping speed in the wide pressure range. The operation of the RCS vacuum system showed that the UHV was rapidly obtained from the atmospheric pressure. It was also shown that the large additional outgassing during the high-power beam operation was promptly evacuated by the TMP. The future operation with more high-beam power requires the vacuum system for the lower pressure region. We have developed a TMP with the rotor of titanium alloy with high mechanical strength. We report the advantages of the TMP in the high-power beam accelerators and the development of the TMP with titanium alloy.