Magnetic field mapping and excitation test in vacuum for the kicker magnet in J-PARC RCS

Kamiya, Junichiro   ; Kinsho, Michikazu  ; Kuramochi, Masaya; Takayanagi, Tomohiro   ; Takeda, Osamu; Ueno, Tomoaki; Watanabe, Masao  ; Yamamoto, Kazami   ; Yamazaki, Yoshio ; Yoshimoto, Masahiro  

The kicker magnets are installed in the extraction section in the Rapid Cycling Synchrotron (RCS) of J-PARC and they extract a proton beam accelerated up to 3 GeV. We performed the mapping in the air applying one third of operational voltage after checking linear dependence of magnetic field with excitation current. A short search coil with the 3-axias stage was used to measure the magnetic field distribution. The results showed that the distribution in the medium plane of the same type of kicker magnet is in good agreement with each other. The excitation test with the operational charging voltage of 60 kV was also performed in a vacuum. At the first stage, we were bothered by the electric breakdown. It was noticed that the reduction of outgassing rate by baking is very effective to suppress the discharge. Pressure and mass spectrum measured during the excitation test showed that the excitation of the kicker magnet has conditioning effect.