The investigation described in this paper dealt with spectroscopic measurements of the near-cathode plasma in a low-pressure arc on a Mg cathode with a current of 100 A and a pulse of duration 150 µs. Information on the directed velocities of the heavy particles (ions and neutral species) has been obtained from measuring the Doppler shift and the broadening of the spectral lines. The electron density in the cathode flare has been estimated from the collisional broadening of the lines. The experimental data obtained support the validity of the potential hump model for treating the mechanism of fast-ion generation.

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