A SIMPLE METHOD FOR THE MEASUREMENT OF THE ELECTRON-TEMPERATURE IN A HELIUM PLASMA BY MEANS OF LASER ATOMIC-ABSORPTION SPECTROSCOPY

It is shown that, for plasmas in which electron-atom collisions domina te over other collision processes, the electron temperature can be der ived from the density of metastable helium states measured with laser atomic absorption spectroscopy. The model describing the electron temp erature as a function of the density of the metastable helium states i s independent of the electron density and is valid for electron temper atures T-e= 2-10 eV and for electron densities n(e) less than or equal to 5 x 10(14) cm(-3) to within an error of 20%. For an extended param eter range a more complex model, additionally requiring knowledge of t he electron density, may be used.