Plasma characteristics of a tapered coaxial gun and its damage effect on tungsten target

Abstract

• A tapered coaxial plasma gun with negative pulse was used to obtain more suitable plasma parameters for simulation of the Type- I ELM in tokamak. • The plasma parameters of the tapered coaxial gun were measured. The characteristics of plasma are analyzed. • Fusion plasma surface interactions relevant results were provided. Damage effect on target was analyzed. Due to the property of high energy density, temperature and density, the plasma prodced by the coaxial gun is usually untilized to simulate the Type- I ELM in tokamak. In this work, the plasma characteristics of a tapered coaxial gun was studied and its effect on the tungsten target was investigated. By using current probe, photodetector, spectrometer and calorimeter, it is found that the plasma energy density, density and velocity increase obviously with the discharge voltage. The maximum energy density could reach 1.4 MJ/m 2 , the maximum electron density could reach 3 × 10 15 /cm 3 , and the maximum ion kinetic energy could reach 113 eV at the voltage of 16 kV, which is suitable for simulating the type I Elms in Tokamak. After one shot, there are many cracks and ablative spots on the surface of W target. Whose size could reach ∼ μm by scanning electron microscope(SEM), this is because W material will become brittle after the frequent heating and cooling alternations under thermal shock and the melt motion driven by high plasma pressure gradient. With the Energy Dispersive Spectrometer(EDS), it can be seen that no matter from the cracks and other area of the surface after one shot, the impurity can be ignored. These results help us to better understand the damage effect of tungsten target for further research.