Nature of Deviations From the Regularities of Three-Particle Recombination in Dense Plasma

Abstract

An explanation is proposed for the phenomenon of deviations from the functional laws of three-particle recombination in dense electric arc plasma of argon at an initial electron density of ~ 1016 cm-3. Experimental data, which are the basis of the work, were obtained by spectral and probe methods during the study of plasma decay of a microsecond pulse electric arc in argon 6 µs at an initial pressure of 70...700 Pa and a discharge current amplitude of 6 kA. Theoretical estimates show that the reason of the observed effects is the self-absorption of resonant spectral lines of argon, which significantly limits the recombination flow of electrons in the energy structure of atoms.

Structure and local parameters of self-compressed plasma streams in external magnetic field

“…However, the value of the ion saturation current measured by the probe turned out to be lower than Langmuir's current due to the attenuation in the near-probe sheath. Such attenuation was also reported in certain studies [14,15], although other studies suggest that the apparent electron temperature might be overestimated [16]. In the case when the electron energy distribution function (EEDF) is bi-Maxwellian with two well--separated temperatures [17], the results can be obtained by straight-line fi ts on the semi-logarithmic current-voltage characteristic.…”

“…The results of the double electric probe measurements should be interpreted with respect to the regime of operation that depends on plasma density, temperature, density of neutral atoms, and magnetic fi eld magnitude. As has been noted above, under the conditions of the MPC discharge, a double cylindrical probe operates in the diffusion regime typical for dense plasma [13][14][15][16]. In this case, the mean free path () is much smaller than the probe radius (R p ) and ionization length (L i ).…”

“…In order to be able to conduct local measurements, we have designed a set of magnetic and double electric probes [11,12]. Double electric probes are very useful for measurements of the electron temperature with good temporal and spatial resolution in various devices [13][14][15][16]. The advantage of a double probe is that it does not require a reference electrode, decreases plasma perturbations, and limits collected current to the ion saturation current [16].…”