Beam uniformization using multipole magnets at the JAEA AVF cyclotron

原子力機構AVFサイクロトロンにおける多重極電磁石を用いたビーム均一化システム

百合 庸介; 石坂 知久; 湯山 貴裕; 奥村 進; 石堀 郁夫; 宮脇 信正; 倉島 俊; 吉田 健一; 柏木 啓次; 上松 敬; 奈良 孝幸

Yuri, Yosuke; Ishizaka, Tomohisa; Yuyama, Takahiro; Okumura, Susumu; Ishibori, Ikuo; Miyawaki, Nobumasa; Kurashima, Satoshi; Yoshida, Kenichi; Kashiwagi, Hirotsugu; Agematsu, Takashi; Nara, Takayuki

It has been known that uniformization of a beam with a Gaussian profile is possible utilizing odd-order nonlinear forces. Here, we investigate uniformization of the transverse beam profile using nonlinear focusing forces produced by multipole magnets, including even-order forces. The result demonstrates a potential to uniformize an asymmetric beam as well as a Gaussian beam by making a combination of the even and odd-order nonlinear forces. Such a combination technique enables us to perform high-uniformity irradiation at a constant particle fluence rate over the whole area of a large target. A research and development on the beam uniformization system composed of sextupole and octupole magnets is now in progress at the JAEA AVF cyclotron facility. Some results of preliminary experiments are also reported.