Electric Discharge Suppression by Outgassing Reduction from Kicker Magnet of J-PARC RCS

摘要

Kicker magnets in rapid cycling synchrotron (RCS) of Japan proton accelerator research complex (J-PARC) are now under construction. Extraction kicker magnets are short pulse magnets with high charging voltage of more then 60 kV which is installing in vacuum chambers. They mainly consist of aluminum alloy as electric plates and ferrites as magnetic cores. Outgassing reduction from those components is very important to prevent not only electrical discharge but also interaction between the proton beam and residual gas in the vacuum. Some structures of the magnet were improved to suppress discharge. We thoroughly reduced outgassing from the components. Surface of the aluminum alloy was finished by pit-free electropolishing. Aluminum alloy and ferrites cores were baked under vacuum before construction of the magnet. They were baked each other until water, which was the main component of outgassing, was reduced. As a result, outgassing rates of the aluminum alloy and ferrite cores were reduced less than 10^-9 and 10^-6 Pa m/sec, respectively. We construct the system which is baked any time as needed by micro heaters directory mounted on the chambers.