Radial and axial distributions of the electron density and temperature in a cascade arc plasma

摘要

Plasmas produced with cascade arcs at atmospheric pressure are supposedly in a state of local thermal equilibrium, or close to it. If we exclude near-electrode regions, the arc can be described as being cylindrically symmetric. In one-component plasmas, the uniformity of the plasma column along the arc axis can also be assumed. In many-component plasmas, due to the demixing effect there are spatial nonuniformities in the plasma composition. Gradients of plasma composition are connected with the gradients in other plasma parameters -- temperature and electron density. In the experiment described in this paper, the plasma gas consisted mainly of helium, with additions of argon. Registration of the spectrum was performed in a side-on configuration, measuring the light emitted by the plasma between arc segments, emerging through slits in the separating insulating rings. The electron density profiles were calculated from measured H_(alpha) linewidths.