Ablation of cathode material heated by high current, high energy transient arcs under different ambient pressure

This study investigates the evolution of transient arc plasma and its ablation behavior of cathode (initial) material under high-power electric pulse, addressing the issue of material ablation control arising from localized thermal gradients and phase transitions during plasma-condensed-matter interactions. Experiments were conducted using a pin-plate gas gap breakdown at varying ambient pressures. The discharge process was diagnosed using synchronized high-speed photography and voltage/current/photoelectric probes. Following discharge channel formation, plasma expansion was observed with an initial velocity of 2-3 km/s, evolving from a spherical shape into an inverted bell shape, subsequently contracting into an inverted funnel configuration, accompanied by the plasma ejection in form of electrode spots. Increasing the discharge current from 15.4 kA to 21.9 kA resulted in a ~90 % increase in plasma radiation intensity. Reducing the ambient pressure led to increased dispersion and weakened radiation intensity of the plasma channel. Post-discharge ablation morphology observations revealed concentrated ablation with distinct regions at 0.1 MPa. pressure, contrasting with a speckle pattern and significantly reduced surface roughness (Ra decreasing from ~2.5 μm to < 0.5 μm) at lower pressure of 0.02 MPa. Inspired by these findings, the study explored and validated the arc-root dispersion effect and ablation homogenization capability of metal foams.