[15p-D209-1~12] 7.2 Applications and technologies of electron beams

[15p-D209-5] Lattice defects in Ice by pulsed electron irradiation

〇Hiroto Ito¹, Thi Mai Dung Do¹, Hisayuki Suematsu¹, Takashi Kikuchi¹, Tadachika Nakayama¹, Go Imada² (1.Nagaoka Univ. Tech., 2.Niigata Inst. Tech.)

Keywords:irradiation damage, electron beam

A brownish material on the surface of Europa, a satellite of Jupiter, was detected by the Galileo spacecraft and is claimed to be newly irradiated NaCl1) . When alkali halides are irradiated with ionizing radiation such as X-rays and electron beams, point defects called F and F2 centers are formed and become colored. The Jupiter's magnetosphere is a plasma sheet that changes from moment to moment, and it is thought that accelerated electrons collide with Europa's surface at different fluxes. If the recovery process of point defects is clarified, the color change due to the increase or decrease of flux can be estimated, and the presence or absence of NaCl can be clarified. To obtain data that can be used as a basis for estimating the color change, pulsed intense relativistic electron beam (PIREB) irradiation was performed on ice. Irradiation damage to ice has been reported in the past2) . 2) Irradiation damage to ice has been reported in the past2) , but only for thin ice. The ice layer on Europa's surface is said to be about 3~4 km thick. Therefore, in this study, PIREB irradiation of ice blocks was performed. As a result, we were able to observe the temperature-independent effect of the electron beam on the ice.