Countermeasure of the multipactor at SDTL cavity in J-PARC Linac

Ito, Takashi  ; Hirano, Koichiro  ; Sugimura, Takashi*; Nammo, Kesao*

The Japan Proton Accelerator Research Complex (J-PARC) facilities were extensively damaged by the Great East Japan Earthquake on March 2011. We restarted the beam operation in December 2011 after the recovery works. However, a multipactor problem of SDTL5B cavity was occurred after the beam restoration. To solve this problem, we performed the analysis of the impurities on the inner surface of the cavity, adopted the countermeasure that is the improvement of the vacuum condition of the cavity and performed the conditioning of the cavity carefully in the summer maintenance period of 2012. By adopting the countermeasure and conditioning, the multipactor problem improved just after the beam restoration and the operation power had been decreased. We present the result of the countermeasures and the present operation status of the SDTL5 in this report.