Electrode erosion and lifetime of field-distortion spark gap switches under 88-kA repetitive discharges.

This paper systematically investigates the electrode erosion and lifetime characteristics of a three-electrode field-distortion spark gap switch operating at a charging voltage of 4 kV and a peak current of ∼88 kA. Lifetime testing was combined with electrode mass measurements and staged macro- and microscopic characterization to identify the principal degradation processes. The switch exhibits a reproducible non-monotonic delay evolution that correlates with the formation, displacement, and blunting of a cathode surface protrusion. The electrodes exhibit an overall net mass loss, while small early-stage fluctuations may result from material redistribution among the electrodes. Scanning electron microscope observations indicate that repetitive localized thermal shock is the fundamental driving force for crack initiation. Spatially nonuniform energy deposition, governed by arc-root attachment and plasma/gas dynamics, produces distinct pit morphologies and thermal-stress distributions. Type II pits tend to aggregate at crack sites and play an increasingly important role in subsequent discharges. The more severe fragmentation on the anode-facing side of the trigger electrode is attributed to greater inferred plasma exposure and energy deposition, which promote type II pit formation, intergranular crack-network development, and eventual fragment detachment. These results provide insight into electrode material selection and lifetime optimization for high-current spark gap switches.