Damage Effects of Ionizing Radiation in Polymer Film Electrets

摘要

Electret sensors or dosimeters can be used to quantify the ionizing radiation dose from charged particles or waves beams (α, β, -e, p etc... γ, X), and with appropriate converters, from fast and slow neutrons. The electret state is reached, by some insulating materials (electrical conductivity lower than 10~(-8) (Ω m)~(-1)), when once charged, the incorporated charge is quasi-permanent ≈ 10~9 s. The charge densities are read (before and after the irradiations) and the radiation dose inferred from the difference between them. PFA (Tetrafluoroethylene-per-fluoromethoxyethylene) and FEP (Tetrafluoroethylene-hexa-fluoropropylene) damage mechanisms were studied bombarding these fluoropolymers with: 1 MeV protons at constant current and fluences from 1 × 10~(11) tower 1 × 10~(16) ions/cm~2, ~(60)Co gamma and X-rays, respectively of 1.25 and 0.106 MeV for absorbed doses of 0.5, 1.0, 8,0 and 100 Gy. The emission of chemical species was monitored with a Residual Gas Analyzer (RGA), during proton bombardment and techniques of Optical Absorption Photospectrometry (OAP), Fourier Transform Infrared (FTIR) and Micro-Raman spectroscopy were used to analyze the virgin, exposed and irradiated films.