Phase bunching in the central region of the JAEA AVF cyclotron for heavy-ion acceleration in the third-harmonic mode

第3加速ハーモニックモードにおける重イオン加速のためのJAEA AVFサイクロトロンの中心領域の位相バンチング

宮脇 信正; 倉島 俊; 柏木 啓次; 奥村 進; 福田 光宏*

Miyawaki, Nobumasa; Kurashima, Satoshi; Kashiwagi, Hirotsugu; Okumura, Susumu; Fukuda, Mitsuhiro*

Phase bunching in the central region of the JAEA AVF cyclotron for heavy ion acceleration in the third-harmonic mode ( = 3) was studied using both calculation with a simplified geometric trajectory model and measurement of an internal beam phase distribution. The phase bunching for = 3 was compared with that for = 2, where the geometric condition of the central region differs from that for the former. The result of measurement shows that the phase bunching for = 3 was equivalent to that for = 2 when a beam buncher was not used before the acceleration. When the beam buncher was active, however, the phase width for = 3 was larger than that for = 2. The analyses using both the calculation and the measurement indicates that, in order to enhance the phase bunching for = 3, it is necessary to modify the geometric condition of the central region and to increase the ratio of a peak dee-voltage to an extraction voltage of an ion source, which is one of the parameters determining the phase bunching performance.