On the gas ionization at the initial stage of a toroidal discharge

Results of the experimental investigation of gas ionization in the ''Uragan'' stellarator in the tokamak and stellarator modes are presented and their comparison with a simplified theoretical model based on the supposition on Maxwell function of electron velocity distribution is conducted. It is stated that the experimental results for the phase of gas break-down (ionization degree K << 1), in which the main part is played by electron collisions with neutral particles, only qualitatively agree with the theoretical model. The experimental data for the phase of the main gas ionization (K > or approximately 0.1) well agree with theoretical predictions