Experimental Study of Millisecond Repetitive Capillary Discharge Plasma Characteristics for Simulating ITER-Like Transient Heat Load

The Type-I edge-localized mode (ELM) is one of the transient events threatening the first wall, with the heat flux $\sim $ GW $\cdot ~\text{m}^{-2}$ , duration 0.5-1.0 ms, and the frequency 1-10 Hz expected in international thermonuclear experimental reactor (ITER)-like Tokamak. First, a millisecond pulsed repetitive plasma generator based on capillary discharge is designed to produce high heat flux plasma for simulating ELM heat load. Then, experimental study is carried out on the plasma discharge characteristics, jet morphology, and plasma parameters under different capillary diameters and materials, which shows that the central heat flux is 0.8-1.31 GW $\cdot ~\text{m}^{-2}$ , with the plasma temperature 1.16-1.25 eV and electron density 5.19- $9.12\times 10^{22}\,\,\text{m}^{-3}$. It also shows that the discharge characteristics and plasma parameters of polycarbonate (PC) are less affected by the capillary diameter than polyethylene (PE), which is mainly due to the higher average ionization energy for PC, indicating that PC capillaries are more appropriate for repetitive pulsed discharge. The research can provide basic parameters and material selection guidance for repetitive capillary plasma generator to produce transient high heat load.