Microwave Discharge in Gas above Regolith Surface

— A layer of regolith with a 1.35% Al content was irradiated from the side of the reactor supporting plate with a microwave pulse with an intensity of 10–15 kW cm –2 (the wavelength is 4 mm) and a duration of 1.5 ms and 3.5 ms. An air rarefaction of ~76 Torr was created in the reactor. A gas discharge occurred when the ratio E 0 / N 0 = 1.03 × 10 –15 V cm 2 was exceeded ( E 0 is the electric field at the reactor axis, N 0 is the concentration of molecules in air). The discharge above the regolith surface occurred only after microwave breakdown of the air with a delay of more than 200 μs. In this case, evaporation of regolith particles and their ejection into the reactor volume took place. It was found that an increase in the microwave pulse duration to 3.5 ms leads to long-term sparking of regolith particles. This can be explained by the energy release during the reaction 2Al + 3FeO → Al 2 O 3 + 3Fe initiated by the evaporation of iron oxide under the combined action of microwave radiation and UV radiation from the gas discharge.