Influence of a non-stationary magnetic field on the charge composition and energy distribution of ions of the cathode plasma of a vacuum arc

The influence of an external non-stationary axial magnetic field on the charge composition and energy distribution of ions of various ionization degree in the cathode plasma jet of a pulsed vacuum-arc discharge in the axial direction has been studied by the method of mass-energy analysis. In the experiment a gallium cathode was used in the liquid-phase state, which made it possible to stabilize the cathode surface during the experiment. The discharge current pulse of a quasi-rectangular shape was synchronized with the harmonic pulse of the coil current generating the axial magnetic field so that the discharge proceeded at the stages of growth, decline, and also during the period of reaching the maximum current in the coil. It was found that the number of ions of each ionization degree and their average energy, as well as the average particle charge, increase in the following order: a discharge in the absence of a magnetic field, under conditions of an increasing magnetic field, a decreasing field, and, finally, at the maximum of the magnetic field. The presented data suggest that the role of induction mechanisms of plasma acceleration is insignificant. Moreover, the excitation of induction countercurrents in the peripheral plasma layers weakens the increase of the magnetic field in the axial region of the plasma, which can be the reason for the opposite effect of the influence of the alternating magnetic field on the charge composition and energy distribution of ions.

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