Radiation-Induced Conductivity of Polyimide Under Monochromatic X-Ray Irradiation: Calculation, Numerical Simulation, and Measurement

X-ray irradiation on dielectric materials will affect their electrical properties, reducing the service life of the equipment. Therefore, calculating and measuring the radiation-induced conductivity is of tremendous significance in studying the radiation effects of dielectric materials. For the research requirements of detector calibration and numerical calculation of radiation-induced conductivity, the generation method of quasi-monochromatic X-ray is studied. The geometric model is established, and the Monte Carlo numerical simulations of the emitted energy spectrum and the photon numbers are carried out. A steady-state quasi-monochromatic X-ray conductivity measurement system was built to test polyimide materials. Experiments show that under a strong electric field and quasi-monochromatic X-ray, the volume conductivity of the sample can rise to 10−16– $10^{-15}\,\,\Omega ^{-1} \cdot \text { cm}^{-1}$ . The radiation-induced conductivity is in the order of $10^{-16}\,\,\Omega ^{-1} \cdot \text { cm}^{-1}$ and increases with the X-ray intensity. The Rose-Fowler-Vaisberg (RFV) model is discretized for MATLAB numerical calculation. The radiation-induced conductivity of polyimide material is calculated based on the model under specified X-ray energy and X-ray tube current. The calculated results are consistent with the experimental results using the given parameters. The radiation-induced conductivity increases linearly with the increase of X-ray intensity.

I. Introduction

With the development of space technology, many aircraft electronic equipment and systems are under the threat of space radiation environment [1], [2]. With the increased operating voltage, the probability of insulation medium damage increases correspondingly in spacecraft. The coupling effect of high voltage and high energy particles jointly affects the dielectric charge and discharge process, increasing the probability of material breakdown, which puts forward higher requirements for the design of insulating materials and radiation-resistant structures [3].