Beam test of sawtooth-wave pre-buncher coupled to a multilayer chopper

鋸歯状高周波を用いたバンチャーシステムの試験と多層式チョッパーの開発

岡田 雅之*; 石山 博恒*; 片山 一郎*; 宮武 宇也*; 仁木 和昭*; 渡辺 裕*; 牧井 宏之   ; 新井 重昭*

Okada, Masashi*; Ishiyama, Hironobu*; Katayama, Ichiro*; Miyatake, Hiroari*; Niki, Kazuaki*; Watanabe, Yutaka*; Makii, Hiroyuki; Arai, Shigeaki*

In TRIAC (Tokai Radioactive Ion Accelerator Complex), intense bunched beams are planned for measurements of C() reactions. For 2-4 MHz bunching to the 26 MHz linac beams, sawtooth-wave pre-buncher has been developed. Since the wave applied to the pre-buncher is pseudo sawtooth shape synthesized from three sine waves, particles in out-of-bunch phase become backgrounds to the bunched beams. In order to remove them, a multilayer chopper has been newly installed upstream the pre-buncher. The multilayer chopper has 20 electrodes (40 mm wide, 10 mm long, and 0.1 mm thick) piled up with gaps of 1.9 mm in vertically to the beam direction. And a square-shape electric potential (100 V maximum, 2-4 MHz) is applied to each electrodes alternately. The short gap makes it possible to realize sharp beam-chopping with relatively low electric potential and weak leakage electric field, although beam particles could be lost by 5% or more, since this chopper is set on the way of beams. As a result, the ratio of bunched particles to backgrounds has been improved from 3:1 to 99:1 by the chopper. High intensity beam test by O beam will be also reported.