Effect of a gas-discharge wall cleanning of vacuum chamber on the discharae parameters in the ''Tuman-2A'' tokamak

The effect of gas-discharge cleaning on the discharge parameters in the tokamak TUMAN-2A with a small radius 8 cm and values of toroidal field Bsub(+) <= 10 kGs is investigated. Its application decreases the light impurities flow into plasma approximately 6 times and contributes to discharge obtaining with domination of transport losses. Simultaneously at the given current the temperature in the central part of plasma filament is decreased. As a result of cleaning low value of stability margin could not be obtained, after its application qsub(min) approximately 5 remained. The energy life time in plasma considerably decreased. This is expla.ined by small dimensions of the tokamak and relatively low plasma parameters. This can probably be avoided in a small tokamak s'ubject to operation at high values of toroidal magnetic field, density and temperature of plasma