A Diagnosis method of laser-accelerated protons using CR-39 in a field contaminated by photo-neutrons

Kanasaki, Masato; Fukuda, Yuji; Sakaki, Hironao; Yogo, Akifumi; Jinno, Satoshi   ; Nishiuchi, Mamiko; Matsukawa, Kenya*; Kondo, Kiminori; Oda, Keiji*; Yamauchi, Tomoya*

In laser-driven ion acceleration experiments using the cluster-gas targets, a significant amount of fast electrons, which drives the ion acceleration, are produced along with high energy ions with several-tens of MeV. Fast electrons could produce high energy photons via bremsstrahlung processes. Accordingly, the photons could produce photo-neutrons via a series of photo-nuclear reactions. In order to diagnose the laser-accelerated protons, we have developed the new analysis technique of CR-39 based on the etch pit geometry, which can practically discriminate the genuine etch pits created by laser-accelerated protons from false etch pits created by the photo-neutrons.