The Measurement of Electron Temperature in High Temperature Plasmas

Abstract

The method is based on the simplifying features of helium-like ions and on the rapid establishment of equilibrium between the processes of populating and de-populating the 2³P₂ level The specific mtensity of the emission line 2³S₁-2³P₂ can then be deduced as a function of the electron temperature. In order to test the basic assumption that the electron velocity distribution is Maxwellian for the very fast electrons which produce the atomic excitation, more than one member of the iso-electronic sequence must be studied. Also, an expression containing the relative emission from two members of the sequence eliminates the electron concentration which can only be estimated at present. The intensities of C V and BIV lines from SCEPTRE IIIA were measured with a combination of a monochromator and a photomultiplier. A carbon arc was used to calibrate the intensities absolutely, and the spatial intensity distribution was determined by means of the Abel integral equation. For typical discharge conditions, the maximum electron temperature attained was in the range (2-3) × 10⁵degK The electron temperature was unaltered by the introduction of the methane. The results suggest that any existing departure from a Maxwellian distribution of electron velocities did not seriously affect the value of electron temperature derived by this method.