An Electric Stress-Pulse Technique for The Measurement of Charges in A Plastic Plate Irradiated by an Electron Beam

The distribution profile and quantity of charges in insulators have been studied by various methods, some of them utilizing thermal, mechanical, and electrical stimulations. A new method, incorporating pulse electric stimulations and pulse acoustic detection, is reported here along with preliminary results of the measurement of the amount and approximate distribution profile of charges in electron-beam irradiated polymethyl methacrylate (PMMA) samples. The amount and the mean penetration depth of charges in the sample are obtained from the height of the first acoustic signals produced in response to a HV impulse applied to the sample. A 5 mm thick PMMA plate irradiated with a 1 MeV electrons at 0.5 to 3.0 Mrad was found to trap charges of approximately -0.3 ¿C/cm2 at a mean depth of about 2 mm.