Design of a wide energy range stacked CR-39 detector diminishing contaminant photo-neutrons using Monte Carlo particle transport simulations

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

A CR-39 detector has been widely utilized in the laser-driven ion acceleration experiments. In our experiments applying cluster-gas target, along with high energy ions with several tens of MeV, a significant amount of well-collimated high energy electrons with similar energies are produced. Such fast electrons could produce high energy photons. Furthermore, such photons could produce photo-neutrons. If the CR-39 is exposed to such photo-neutrons, it can record recoiled protons and other heavy ions generated by the photo-neutrons. In order to precisely diagnose only for laser accelerated protons and heavy ions, we have to keep the photo-neutron fluence level as low as possible. In the present study, to minimize the effect of photo-neutrons, we have optimized the geometry of the CR-39 detector unit by using Monte Carlo particle transport code PHITS. The developed detector unit allows us to diagnose the laser-accelerated ions up to several hundred MeV with less effect from photo-neutrons.