Measurements of Space Charge Distributions in PMMA

Spontaneous dielectric failure can be precipitated by space charge accumulation when dielectric materials are exposed to charged particle irradiation. Events of this nature are believed to occur in satellite dielectrics. This has prompted a need for a method of measuring charge accumulation in bulk dielectric samples when exposed to charged particle irradiation, even in the presence of surface ion neutralization. A Pulsed Electro Acoustic (PEA) system has been constructed to this end. 2.5 cm thick, polymethyl Methacrylate (PMMA) sheets were charged by a 6 MeV nominal electron beam and interrogated by the PEA system. These experimental results were also compared to Monte Carlo radiation transport results with imposed internal electric fields due to the space charge.