Characteristics of a Repetitive Pulsed Capillary Discharge Helium Plasma Source and Its Interaction With Tungsten-Based Materials

The divertor material will be subjected to a high heat flux helium plasma with a repetition rate of 10 Hz. This work investigates a repetitive helium plasma source based on pulsed capillary discharge, where helium is ionized and Joule-heated by high-voltage pulses, then confined by the capillary to form a transient high-density plasma jet (duration: 1 ms, density: ~ 10²² m⁻³). Plasma parameters were measured using a combined spectroscopic and high-speed imaging diagnostic system. The variation of plasma parameters with capillary peak current and pressure was further investigated to accurately control plasma parameters. Subsequently, the ablation behavior of tungsten under the generated repetitive-frequency heat flux was analyzed. The experimental results demonstrate that the heat flux ranged from 0.13 to 1.37 GW · m⁻² under different peak current and pressure conditions. Under the high heat flux with helium, tungsten surfaces exhibited rapid helium-induced modifications, including bubble formation, pore development, and nanostructure evolution within a millisecond timescale. The observed correlation between incident heat flux magnitude and surface degradation rate suggests that thermal loading serves as a critical accelerator for helium-induced material modification in fusion-relevant conditions.