Cathode and plasma phenomena in vacuum-arc sources of hydrogen isotope ions. II. Ionization processes in the arc plasma

Abstract

An experimental and theoretical study of the content of deuterium ions in arc discharge plasma was performed for deuterated zirconium cathodes. It was found experimentally that the deuterium ion percentage increased significantly with increasing arc current and decreasing arc duration, reaching 85% at kiloampere currents and few microsecond durations. In this case, a clear correlation was found between the content of deuterium ions in the arc plasma and the mean charge of zirconium ions: the higher the mean Zr ion charge, the greater the amount of deuterium ions in the plasma. A model was developed to describe the ionization processes that occur in the plasma of a vacuum arc with a deuterated cathode. It was shown that the relative content of deuterium ions in the plasma jet ejected from an individual cathode spot cell is not over 50%. The deuterium atoms are additionally ionized when the plasma jets of individual cells are mixed within a group cathode spot with high average current density. Conditions for additional ionization arise when the density of cells on the cathode surface is high, that is, at the initial stage of the discharge operation.

Determination of the critical temperature of Nb–Al alloys from the plasma parameters of a vacuum arc cathode spot

“…The plasma ion kinetic energy E kin ≈ 100 T cr (equation ( 1)) can be directly estimated from the critical state of matter during the explosion, while a coefficient about '100' corresponds to additional plasma acceleration as the cathode flame expands, and fully agrees with the results of MHD and kinetic calculations [13][14][15][16][17].…”

“…The empirical ratios for the average charge [9] and for the cathode potential fall-'cohesive energy rule' [10] were obtained. At the theory progress and numerical simulation, the initiation conditions of explosive pulses were determined [11,12], as well as hydrodynamic and kinetic of the expanding plasma was described in detail [13][14][15][16][17] etc. However, there is still no explanation of these ratios.…”

Three-fluid simulation of a cathode spot jet in vacuum arc discharge with a metal deuteride cathode

“…So the plasma can be described using the three-fluid approximation. This assumption is justified by the fact that in dense near-cathode plasmas (~10 26 m −3 ), there is a strong particle collision process [11,13]. 3.…”

“…Finally, the boundary conditions on the cathode spot (OD) are very important. According to the literature [7,11,13], the evaporated atoms of Ti and D on the cathode spot are assumed to be subsonic. For the inlet (cathode spot) condition of subsonic flow, the ion total pressure, the ion total temperature and the direction of plasma flow should be specified.…”

“…The model neglected the dissociation process of D molecules. Recently, Barengolts et al [13] further improved this model by considering D molecules as a fourth fluid, so it is able to simulate the dissociation process of D molecules. However, the 1D model ignored the rapid plasma expansion in the radial direction, which may lead to an overestimation of the electron impact ionization effect.…”