Characteristics of a repetitive ELM-like pulsed plasma source and its damage effects on tungsten target

This paper comprehensively analyzes the application of coaxial gun discharge plasma in the direction of nuclear fusion candidate materials. The detailed design of the plasma source and its parameters meet the requirements of the mitigated ELMs-I transient thermal load simulation experiment. • A compact-sized repetitive discharge coaxial gun plasma source is developed in order to simulate transient heat loads (ELMs-I) in ITER. • The gun produces helium plasma with an electron density of 1.6-2.0 × 10 15 cm −3 , an energy density of 0.2 MJ/m 2 , and a pulse width of 0.6 ms. • It is found that the heat accumulation effect and thermal stress on the surface of tungsten target are intensified with the increase of shock frequency. High-frequency thermal shocks led to enhanced melting and accelerated crack propagation. Transient thermal load events have great effects on the service life of plasma-facing materials (PFCs) in tokamak steady-state operation. A compact-sized repetitive discharge coaxial gun plasma source is developed in order to simulate transient heat loads such as type I edge-localized modes (ELMs-I) in ITER. In this paper, the plasma characteristics of repeated coaxial gun and the damage effects of different frequencies on tungsten target are studied. At a constant initial condition (charging voltage, gas-flow), the voltage and current data reflects the discharge characteristics of the repeating plasma source. The gun produces helium plasma with an electron density of 1.6–2.0 × 10 15 cm −3 , an energy density of 0.2 MJ/m 2 , and a pulse width of 0.6 ms. The local surface heating evolution of W is clearly observed with the camera during repeated pulsed plasma exposure. By changing the discharge frequency of coaxial gun, it is found that the heat accumulation effect and thermal stress on the surface of tungsten target are intensified with the increase of shock frequency. High-frequency thermal shocks led to enhanced melting and accelerated crack propagation, with residual stresses on the target surface being released through crack formation. The simulation experiment results provide valuable insights into the interaction mechanisms between plasma and the first wall material at different frequencies in tokamaks.