Highly Ionized Helium Arc Plasma. Determination of the Temperature in Nonequilibrium Conditions and the Effect of Plasma Microfields

Abstract

Methods are proposed for the spectral measurement of electron temperature Т_е in a highly ionized nonequilibrium He plasma at atmospheric pressure based on a comparison of the intensities of atomic and ionic lines with a whole complex of experimental data (primarily, n_e). The large energy gap between the emitting HeI and HeII excited levels (of more than 50 eV) and allowance for the nonequilibrium manifested in the overpopulation of the atomic levels with respect to the ionic levels make it possible to make reliable and simple Т_е estimates, especially if the ionization energies of the emitting levels of the atom and the ion are close. For practical use, three pairs of HeI and HeII lines observed in the spectral range of 200–1100 nm are recommended. The radial and temporal (upon the quasistationary pulsed heating of the electric arc plasma) dependences of Т_е are obtained in the range of axial values of 3.2–4.7 eV.