Conditioning of the Tokamak Vacuum Chamber with Reactor Technologies

Abstract

The article describes a method of conditioning the plasma-facing surfaces of a vacuum chamber. Efficient conditioning of surfaces is an important aspect for achieving maximum plasma parameters and minimizing the number of discharge failures. A simple method of conditioning is to heat the chamber to the required temperatures. For example, in order to remove water from the surface and desorb hydrogen and deuterium from carbon-containing structures, the chamber in tokamaks is heated to temperatures of 150–400°C. However, for the Tokamak with Reactor Technologies (TRT) with a superconducting electromagnetic system, this method of conditioning has certain limitations. In order to reduce the heat fluxes to the coils of the electromagnetic system, cooled screens are placed around the vacuum chamber and nozzles, which reduce the heat fluxes by 100 times; therefore, conditioning of the vacuum chamber of the TRT by means of a glow discharge becomes preferable. The modes of glow discharge in helium and hydrogen are investigated, and their optimal conditions are determined (P ~ 4 mTorr, I = 12 A). The process of chamber cleaning is most effective in the glow H₂ discharge at chamber surface temperatures T < 100°C, which can be confirmed by mass spectrometric and Auger measurements.