Reduction of outgassing from the ferrite cores in the kicker magnet of J-PARC 3-GeV rapid cycling synchrotron

Ogiwara, Norio; Suganuma, Kazuaki ; Hikichi, Yusuke; Nishikawa, Masaaki; Yanagibashi, Toru; Kamiya, Junichiro   ; Kinsho, Michikazu  

Kicker magnets are used to kick out the accelerated beam to the transport lines in the RCS of the J-PARC. A high voltage is applied to kickers for a short period, so they must be installed in a vacuum to prevent discharge. Therefore, it is important to reduce the outgassing of water vapor from the ferrite cores. This time, we have decided to construct the reserve magnets with very low outgassing at high-voltage discharge. First of all, the thermal desorption behavior of the ferrite was investigated by thermal desorption spectroscopy (TDS). TDS spectra show two peaks of water vapor: at 150C and 300C. Carbon dioxide is rather largely emitted with the peak around 275C and then decreases with the temperature. From these results, the ferrite cores were vacuum-fired at 450C for 48 h. Then the good properties for the magnetic cores were confirmed. And now the performances of the kicker magnet are examined.