Beam development for flat-top acceleration in the JAERI AVF cyclotron

Kurashima, Satoshi; Miyawaki, Nobumasa; Fukuda, Mitsuhiro; Okumura, Susumu; Nara, Takayuki; Agematsu, Takashi; Ishibori, Ikuo; Yoshida, Kenichi; Nakamura, Yoshiteru; Arakawa, Kazuo

The JAERI AVF cyclotron provides a variety of ion beams especially for the research in biotechnology and materials science. Several cyclotron technologies such as cocktail beam acceleration, a uniform irradiation in a wide area and beam pulsation have been developed so far. A flat-top acceleration system for the JAERI AVF cyclotron has been designed to minimize the energy spread mainly for a microbeam production. The flat-top acceleration using fundamental and fifth-harmonic frequencies for an acceleration voltage is an excellent technique to reduce the energy spread.