The Influence of a Gas Flow on the Efficiency of the Active Spectroscopy Plasma Cleaning System of the Input Mirror of Optical Diagnostics at ITER

The results of a study of the effects of a gas flow through the discharge region and the location of the diagnostic port walls close to the discharge cell on the efficiency of the plasma system for cleaning the entrance mirror of the Active Spectroscopy optical diagnostics, which have been developed in Russia for the ITER reactor, are presented. The experiments were carried out on a full-size functional model of a discharge cell operating on a constant or unipolar pulse current, electrically isolated from the walls of the vacuum chamber. The material of the model of the entrance mirror is molybdenum. The working gas is argon. A vacuum unit with dynamic stabilization of the working gas pressure was used. The absence of a gas flow through the discharge region and the proximity of the ITER diagnostic port walls to the discharge cell were simulated by placing the discharge cell inside a box-shaped gas-dynamic fairing placed in a vacuum chamber. Experiments with a gas flow at a large distance from the discharge cell to the walls of the vacuum chamber were carried out without using a fairing. It was revealed that the absence of a gas flow at a small distance of the discharge cell elements from the walls of the vacuum chamber increases the cleaning efficiency.