Characteristics of X-ray-induced Surface Charge on Alumina Ceramics

The X-ray radiation generated by vacuum interrupters (VIs) has become a subject of growing scientific and engineering concern due to possible cumulative radiation damage to adjacent equipment and human health. In high-voltage VIs, the operational X-ray irradiation dose on ceramic components can reach the order of Sieverts (Sv), potentially inducing significant surface charge accumulation. This study investigates the effects of X-ray irradiation on surface charge characteristics of alumina ceramics, focusing on the interplay between radiation dose and surface roughness. An integrated experimental platform combining isothermal surface potential decay (ISPD) measurements with X-ray irradiation was developed to measure and analyze X-ray-induced charge dynamics under vacuum conditions with the active electrostatic probe method. Results revealed that X-ray exposure modifies trap parameters, increasing both shallow and deep trap levels and densities, which retards surface charge decay. A critical surface roughness threshold of approximately 2 μm is identified, which is valid for the X‑ray energy spectrum used in this study (peak at ∼90 keV, ranging from 50 to 270 keV). For higher X‑ray energies, the threshold roughness becomes significantly larger. Below this value, smoother surfaces facilitated photon penetration and electron emission, leading to higher charge accumulation, while rougher surfaces exhibited charge density saturation due to enhanced electron trapping and recombination. The study provides insights into optimizing ceramic insulators for high-voltage equipment by balancing surface roughness to minimize radiation-induced charge accumulation, enhancing operational reliability in radiation-prone environments.