Progress in formation of single-pulse beams by a chopping system at the JAEA/TIARA facility

原子力機構TIARA施設におけるビームチョッパーを用いたシングルパルスビーム形成技術の進展

倉島 俊; 田口 光正; 石堀 郁夫; 奈良 孝幸; 横田 渉

Kurashima, Satoshi; Taguchi, Mitsumasa; Ishibori, Ikuo; Nara, Takayuki; Yokota, Wataru

The intervals of beam pulses from a cyclotron are generally tens of ns and they are too short for pulse radiolysis experiments which require beam pulses at intervals ranging from 1 s to 1 ms (single-pulse beam). A chopping system, consisting of two types of high voltage kickers, is used at the JAEA AVF cyclotron to form single-pulse beam. The first kicker installed in the injection line generates beam pulses with repetition period of 1 s to 1 ms. The pulse width is about a cycle length of the acceleration frequency. The other kicker in the transport line thins out needless beam pulses caused by multi-turn extraction. We could not provide single-pulse beam stably over 30 min since the magnetic field of the cyclotron gradually decreased by 0.01% and the number of multi-turn extraction increased. The magnetic field was stabilized within 0.001% by keeping temperature of the cyclotron magnet constant. In addition, a new technique to measure and control an acceleration phase has enabled us to reduce the number of multi-turn extraction easier than before. We have succeeded to provide single-pulse beam of a 320 MeV C without retuning of the cyclotron over 4 h, as a result.