A new method of measuring electron temperatures in plasmas in the absence of local thermodynamic equilibrium

Abstract

A new method of measuring electron temperatures in plasmas is described. This uses a property of the pressure broadening by electron impacts of isolated spectral lines, namely the temperature dependence of the shift-to-width ratio. The only requirement is that the electron velocity distribution can be described by a temperature, and no knowledge is required of bound level populations, or of the ionization equilibrium. The observations are made on line radiation, and no intensity calibrations are needed. The physical basis of this technique and validity criteria for its use are given. Limitations of theoretical estimates of line shifts are described. These present no barrier to the method's use. The so-called `plasma polarization' shift is discussed. Experimental results are given which demonstrate the possibilities of making such measurements, and which provide some evidence about the plasma polarization shift.