Development of high power baluns using MA cores, 2

Tamura, Fumihiko   ; Shimada, Taihei ; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu   ; Nomura, Masahiro  ; Toda, Makoto*; Hasegawa, Katsushi*; Hara, Keigo*

In the J-PARC RCS, magnetic alloy (MA) loaded rf cavities are employed to achieve a high accelerating voltage and to realize the dual harmonic operation, where a single cavity is driven by the fundamental accelerating rf and the second harmonic. The cavity is driven by a class-AB push-pull tetrode amplifier. R&D for a high power balun to mitigate the unbalanced output voltages of two tubes is undergoing. The balun is a rf transformer, which consists of a MA core and high voltage cables. In application to the RCS rf system, the maximum rf voltage is very high in the order of 15kV and suppression of corona dischages is a key. We presentthe techniques to suppress corona discharges. Also, the R&D status of cooling of the MA core and cables.