Paper 
Title 
Page 
WEPPT014 
Analysis of Phase Bunching in the Central Region of the JAEA AVF Cyclotron 
350 

 N. Miyawaki, H. Kashiwagi, S. Kurashima, S. Okumura
JAEA/TARRI, Gunmaken, Japan
 M. Fukuda
RCNP, Osaka, Japan



Phase bunching generated in the central region of an AVF cyclotron was estimated by a simplified geometric trajectory analysis model for particles traveling from the first to the second acceleration gap. In principle, a rising slope of a deevoltage at the first acceleration gap is more or less effective for production of the phase bunching. The phase difference between particles at the second acceleration gap depends on combination of four parameters: the acceleration harmonic number (h), a span angle of the dee electrode, a span angle from the first to the second acceleration gap, a ratio between a peak deevoltage and an extraction voltage of an ion source. In the case of the JAEA AVF cyclotron, the effective phase bunching was realized for h = 2 and 3, and the geometric condition of phase bunching was unrealistic for h = 1. An orbit simulation for the JAEA AVF cyclotron indicated that the initial beam phase width of 40 RF degrees for h = 2 was compressed to 11 RF degrees. The phase bunching evaluation based on the simplified geometric trajectory analysis was consistent with the orbit simulation result, and practical phase bunching was verified by beam phase width measurement.


