Regulation of operating conditions in thermonuclear reactors by means of gas absorption

The time required to produce and absorb a hydrogen atmosphere in the vacuum chamber of a tokamak is estimated. The first wall of the tokamak is covered by a layer of titanium containing dissolved hydrogen and the wall temperature can be regulated. It is shown that the formation and absorption time of the hydrogen atmosphere is of the order of a few seconds when an oxide film is present on the titanium surface; in the absence of an oxide film, this time drops to a few milliseconds. In the latter case the hydrogen concentration on the wall-chamber boundary may vary appreciably (in particular, it increases when gas is absorbed). This can result in the formation of hydride films on the surface of the first wall. When an oxide film is present, the hydrogen concentration in the titanium coating does not change significantly during absorption or desorption of the hydrogen in the chamber. The relaxation time of the hydrogen concentration due to diffusion in the titanium layer is approx.0.1--1 s