On the Interaction between a Fully lonized Plasma and a Neutral Gas Blanket

Abstract

Experimental studies have been performed of a fully ionized magnetized plasma generated in a poloidal magnetic field by a transverse electric field applied between two electrodes and being surrounded by a neutral gas blanket: (i)The rotating plasma which has been generated in the crossed fields is released from its energy source and its rotation is being stopped. The plasma decay is then studied in the absence of macroscopic motions, with the exception of those from a slow diffusion process. The state of ionization is determined by suddenly giving the plasma a small pulse of angular momentum which, after a short time is recovered as a current pulse being extracted by means of a short-circuit between the electodes. The pulse becomes a measure of the state of ionization and shows that the rate of penetration of neutral gas into the plasma is strongly delayed at high plasma densities, in agreement with theory. (ii)The velocity field of a quasi-stationary, rotating plasma has been investigated spectroscopically by observing the Doppler shifts of various spectral lines. The results agree with theoretical perdictions of the velocity and temperature distributions within the plasma region. The results also support the prediction that the interior of the plasma should be screened from the surrounding neutral gas.