Experimental study on plasma generated by a tapered coaxial accelerator and its damage effects on a tungsten target at different angles

Abstract

Plasma wall interaction inevitably occurs during the operation of tokamaks. The coaxial gun device has low operation cost and the parameters of plasma produced by the gun are close to those of type I edge localized mode (ELM); therefore, the coaxial gun is suitable in simulation experiments as a heat flux source of transient events such as type I ELM under the condition of H-mode in the International Thermonuclear Experimental Reactor. In this paper, the plasma generated by the discharge of a tapered coaxial accelerator thermal shock on a tungsten target is used to simulate the damage effect of the divertor. The plasma parameters are measured in the experiment. The velocity of the plasma is 41.7 km s−1, and the kinetic energy of a single hydrogen ion is 9.2 eV. The energy density at the center of the plasma can reach 1.5 MJ m−2, and the density can reach about 2.78 × 1015 cm−3. The reflection of plasma in the process of exposure at different angles is observed. It is observed that droplets of millimeter size splash from the target. Traces of liquid flow are observed on the surface of the target, which shows that there is a melting process on the surface of the target. The mass loss of the target is of the order of milligrams after 20 pulses. The ablation and residual stress of the target surface both decrease with a decrease in the angle. This is because the accumulated energy per unit area of the target surface decreases with a decrease in the angle. The results of the simulation experiment help us to understand the working state around the divertor target in tokamak devices.