Identification of high energy ions using backscattered particles in laser-driven ion acceleration with cluster-gas targets

Fukuda, Yuji; Sakaki, Hironao; Kanasaki, Masato; Yogo, Akifumi; Jinno, Satoshi   ; Tampo, Motonobu; Faenov, A. Ya.*; Pikuz, T.; Hayashi, Yukio; Kando, Masaki; Pirozhkov, A. S.; Shimomura, Takuya; Kiriyama, Hiromitsu; Kurashima, Satoshi; Kamiya, Tomihiro; Oda, Keiji*; Yamauchi, Tomoya*; Kondo, Kiminori; Bulanov, S. V.

A new diagnosis method for high energy ions utilizing a single CR-39 detector mounted on plastic plates is demonstrated to identify the presence of the high energy component beyond the CR-39's detection threshold limit. On irradiation with a 25 MeV per nucleon He ion beam from conventional rf-accelerators, a large number of etch pits having elliptical opening shapes are observed on the rear surface. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This ion detection method is applied to laser-driven ion acceleration experiments using cluster-gas targets, and acceleration of ions with energies up to 50 MeV per nucleon are identified.