Research on outgas and light emission from electrostatic discharge on polymer films in vacuum

On the surface of thermal control materials of artificial satellites, the surface discharge occasionally occurs especially on high-altitude orbits. In this paper, emitted light of discharge and outgases in a vacuum chamber are measured to investigate this phenomenon. Samples used for experiments are fluoroethylenepropylene (FEP) and polyethyleneterephthalate (PET) films of 25 μm and 127 μm thick. The released gas from a specimen under irradiation of electron beam increases the pressure around the specimen. The mass spectrum of gas released from the specimens by the discharge shows that water molecules in the chamber diminish after discharges on PET of both thicknesses and 25 μm FEP. It is probable that water molecules are involved in these discharges. The spectrum analyses of emitted light show that at the initial period of a discharge the light emitted from hydrogen atom (Hα) prevails. Comparing FEP and PET, FEP releases less amount of gas after the occurrence of a discharge. Therefore, the concentration of discharge energy might be lower. Especially in case of the surface discharge on 127 μm thick FEP, the small change of the proportion of the light from hydrogen and the small diminution of water coincides. (author)