Processes on the glass surface under irradiation with medium-energy electrons

The results of experimental studies of the processes occurring on the surface of protective glasses of solar batteries and elements of reflective coatings of high-orbit artificial Earth satellites (AES) under irradiation with electrons with an energy of 30 keV are presented. The studied samples were made on the basis of K-208 glass, while the samples of reflective coatings differed in the presence of silver and stainless steel layers on the reverse surface of the glass plates, deposited sequentially by the magnetron sputtering method. Electron irradiation of the samples was carried out in a vacuum of 10–4 Pa at a particle flux density (φ) from 1·109 to 8·1012 cm–2s–1; the surfaces of the samples before and after irradiation were examined by atomic force microscopy (AFM). On the irradiated surface of glass samples, electrostatic discharges (ESD) arose, the parameters of which were characterized by oscillograms of generated electromagnetic pulses; for elements of reflective coatings, leakage currents to the metal substrate were additionally measured. It was found that changes in the structure of the irradiated surface of the samples are due to the appearance of traces of ESD and the formation of gas-filled bubbles on it, and changes in the back surface of glass plates are caused, presumably, by shock waves formed when ESD occurs on the irradiated surface. The ESD frequency and leakage currents increase with increasing electron flux density in the specified range, but these dependences differ significantly. Measurements at a constant value of φ = 2.0·1010 cm–2s–1 showed that with an increase in the electron fluence from 1014 to 5·1016 cm–2, the ESR frequency increases, but the amplitude of electromagnetic pulses decreases.