Design and test of 2-4 MHz sawtooth-wave pre-buncher for 26 MHz-RFQ

26MHz-RFQ用鋸歯状高周波プリバンチャーの設計と試験

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

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

The measurement of C() reaction is planned at TRIAC (Tokai RadioIsotope Accelerator Complex). An intense pulsed beam with the width of less 10 ns and the interval between 250 ns and 500 ns is required for this experiment. Because the Split Coaxial RFQ(SCRFQ), which is one of the TRIAC accelerators, has a radio frequency of 26 MHz, the bunch interval becomes 38.5 ns. In order to make the bunch interval of 250 ns or more, the pre-buncher with a frequency of 2-4 MHz, is considered to be installed upstream of the SCRFQ. It is designed as the pre-buncher has two gaps with non-Pi mode. In order to make the bunching beam profile like a pseudo sawtooth-wave, the RF voltage synthesized three harmonic frequencies is applied to these gaps. Consequently, the pre-buncher has a compact size and no leakage electric field outside gaps, and can keep the RF voltage low. Recently, the beam test of this pre-buncher with a case of 2 MHz-RF and SCRFQ was performed by using O and C beams. The clear bunch structure with a interval of 500 ns was obtained by the SSD set downstream of the SCRFQ. The results of the beam test are almost consistent with those of the beam simulation code.