HIGH POWER CONDITIONING OF ANNULAR-RING COUPLED STRUCTURES FOR THE J-PARC LINAC

For the energy upgrade of the J-PARC linac, 25 annularring coupled structure modules were fabricated and installed to a beam line. In the high-power conditioning process of these modules, we faced the issue of the unstable operation of a module No. 4. Eventually this issue was naturally resolved, however the cause of this issue was uncertain. To address the cause, we investigated the records of its vacuum pressure with attention to the fluctuations of the vacuum pressure. This result indicates that the pressure fluctuation correlates with operation stability.