Color centers in NaCl single crystals induced by pulsed intense relativistic electron beams to simulate radiation bursts in Europa

Abstract

To simulate the burst irradiation environment of Europa, single crystals of NaCl were irradiated by pulsed intense relativistic electron beams (PIREBs) with a peak energy of 6 MeV, a current of −800 A, and a pulse width of 70 ns. After irradiation, the optical absorption of the samples was measured, and results indicated that the irradiation induced F-and F 2 -centers. The density of F-centers was estimated to be 8.9 × 10 16 cm −3 from 1 shot of PIREB irradiation with 6 MeV. The absorbed energy to form F-centers by PIREB was comparable but slightly higher than those induced by conventional direct current accelerators. The effect of pulsed heating, which should be taken into account for the detection of NaCl on Europa, is discussed.

Mineral Diversity on Europa: Exploration of Phases Formed in the MgSO4–H2SO4–H2O Ternary

“…7,8 However, the stability of this effect over geological time scales has been questioned. 9 As a result of these studies, models of Europa's surface composition are divided into those that are exogenic and those that are endogenic. There is, however, the possibility that the compositions of materials upon Europa are driven by a combination of endogenic and exogenic processes.…”

“…As regards the icy satellites of Jupiter, Europa, Ganymede, and Callisto, the Near-Infrared Mapping Spectrometer carried about the Galileo spacecraft indicated that the surfaces of these worlds are dominated by hydrate materials. Subsequent to this discovery, there emerged two premises as to the nature of these hydrate materials upon the surface of Europa–that they are brines composed within the MgSO 4 –Na 2 SO 4 –H 2 O system originating from Europa’s interior , or that they are sulfuric acid hydrates (solids in the H 2 SO 4 –H 2 O system) with the H 2 SO 4 radiolytically produced from an influx of sulfur from Io. , More recently, NaCl has been suggested as a major component of the surface of Europa, as color centers in this mineral (a result of the radiation environment of the surface) could explain the surface coloration observed by Galileo . , However, the stability of this effect over geological time scales has been questioned . As a result of these studies, models of Europa’s surface composition are divided into those that are exogenic and those that are endogenic.…”

Color centers in K–Na–Cl crystals induced by pulsed intense relativistic electron beam at 77 K

“…In a previous study, the introduction of the color centers and their measurements was carried out using NaCl single crystals as targets at room temperature. 28) The pulse width of the electron beam irradiated to the target in this study was 70 ns, 28) which is short enough to simulate the pulsed irradiation of the surface of Europa. Furthermore, as far as the author's knowledge, there is no report on the irradiation of Na-K-Cl by pulsed electron beams.…”