Electron-beam lunar dust mitigation under solar-like vacuum ultraviolet illumination

Abstract

Electrostatic dust-cleaning with low-energy electron beams is a promising countermeasure against regolith contamination expected during sustained Lunar surface operations. Laboratory demonstrations, however, typically neglect the vacuum ultraviolet (VUV) component of solar radiation that dominates photoelectric charging on the Lunar dayside. Here we quantify, for the first time, the influence of a sun-like VUV spectrum on electron-beam-driven dust removal from spacesuit fabrics. Beta-cloth samples deliberately contaminated with OPRLJSCN Lunar Mare simulant were exposed to (i) a thermionic electron beam (30μA cm−2, ≤ 120 eV) and (ii) VUV fluxes generated by a mixed-gas 13.56 MHz RF plasma lamp that reproduces the solar spectrum in the 115–160 nm range. Three illumination regimes were tested: no VUV (dark), lunar-equivalent VUV (0.3 mW cm−2), and elevated VUV (5 mW cm−2). The inclusion of VUV photons significantly lowered the threshold beam current density and energy to initiate dust mobilisation, with the filament bias needed to initiate lift-off falling from –93 V (dark) to –52 V (lunar-equivalent VUV) and –37 V (elevated VUV), while the required beam current density dropped by up to two orders of magnitude. Dust removal efficiency improved from 76% after 72 s (dark) to 85% in 48 s (lunar VUV) and 95% in only 9 s under strong illumination. Furthermore, the mean particle size reduced with increasing VUV flux from 29μm (brushing) to 16μm (dark). Results indicate that the Solar VUV can be exploited to reduce power requirements and cleaning time for electron-beam dust mitigation, and motivates inclusion of realistic illumination environments in future mitigation trials. Show more