Formation of a uniform ion beam based on nonlinear focusing and its applications at the JAEA TIARA cyclotron

原子力機構TIARAサイクロトロンにおける非線形集束に基づく均一イオンビームの形成と応用

百合 庸介; 湯山 貴裕; 石坂 知久; 吉田 健一; 石堀 郁夫; 奥村 進

Yuri, Yosuke; Yuyama, Takahiro; Ishizaka, Tomohisa; Yoshida, Kenichi; Ishibori, Ikuo; Okumura, Susumu

A formation/irradiation technique of large-area uniform ion beams based on nonlinear focusing of multipole magnets has been developed for advanced research and efficient industrial applications at the AVF cyclotron facility of TIARA. The procedure of the uniform-beam formation is established as follows: First, an ion beam extracted from the cyclotron is multiply scattered with a self-supporting thin foil to smooth out the transverse beam intensity distribution into a Gaussian-like one, which is prerequisite to the formation of a highly uniform ion beam. Then, the tail of the distribution is folded into the inside by the nonlinear force of octupole magnets and the distribution is made uniform on a target. We have realized various uniform beams (over 100 cm in area) of H, C, Ar, and Xe ions with a typical uniformity below 10%. Such large-area uniform beams enabled the suppression of local target heating and efficient low-fluence irradiation, and are applied to a radiation degradation test of space-use solar cells and a study on functional materials to date.