Operational experience of single-ended magnetic alloy cavities at J-PARC RCS

Tamura, Fumihiko   ; Okita, Hidefumi  ; Yamamoto, Masanobu   ; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; Nomura, Masahiro  ; Shimada, Taihei ; Hasegawa, Katsushi*; Hara, Keigo*; Adachi, Kyosuke  

The replacement project for the Magnetic Alloy (MA) cavities of the 3GeV RCS at J-PARC has been underway for several years. The original cavities are the push-pull (PP) configuration, where rf current is supplied alternately from a pair of tetrode tubes to the electrodes on the upstream and downstream sides of the acceleration gap. All cavities are to be replaced with newly developed single-ended (SE) cavities. In PP cavities, significant unbalance in the operation of the upstream and downstream tetrodes due to multiharmonic rf occurs. This unbalance has been one of the limiting factor of beam intensity. This unbalance does not occur essentially in SE cavities. Currently, six of the twelve cavities have been replaced. The SE cavity does not have a configuration to cancel even-order higher harmonics, therefore the harmonic components are different from those of the original PP cavity. We report on the operational experience with the single-ended cavity at the J-PARC RCS.