Single-turn extraction technique for the JAERI AVF cyclotron

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

A flat-top acceleration system using fifth-harmonic frequency for the JAERI AVF cyclotron was developed to minimize the energy spread of an ion beam mainly for microbeam formation with a spot size of 1 micron in diameter by focusing with a set of quadrupole magnets. A single-turn extraction is an indispensable condition to reduce the energy spread without significant beam loss by the flat-top acceleration. In order to save time for the single-turn extraction tuning over measuring time distribution of the beam bunch, a deflector probe has been developed to observe the turn separation and the radial beam width. In this paper, we report the single-turn extraction technique with the deflector probe. As a result of beam developments, the single-turn extraction can be achieved in one or two hours and radioactivity of the deflector electrode can be also reduced in the acceleration of a high energy proton beam.