Development of high power baluns using MA cores

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. In the dual harmonic operation, the output voltages of two tubes are unbalanced. By the unbalanced output voltage, we observe an increase of screen grid current of one of the tubes, and power consumption of the cavity tanks are also unbalanced. To balance the output voltage, high power baluns using MA cores are under development. We present the design of the baluns and test results using the RCS rf system.