Measuring the electron temperature of a powerful pulsed discharge

The electron temperature of a plasma (Ne ∼ 1017 cm−3) produced by a powerful pulsed discharge was measured by the relative intensity of the spectral lines from lithium-like impurity ions (NV, OVI). For such calculations it is necessary to know the population of the different ionic levels; this was found by solving a system of balance equations describing the processes which give rise to population and depopulation of levels. It has been found that under experimental conditions (Ne ∼ 1017 cm−3) the population of the lower levels of the ions under consideration is close to a Boltzmann population, relative to the ground state. The higher levels are in thermodynamic equilibrium with continuum but the population of these levels, relative to the ground state, is considerably smaller than a Boltzmann population. Calculations have been made of the α-corrections which show the deviation from a Boltzmann population relative to the ground state. With these corrections it was possible to obtain internally consistent values of the electron temperature (Te ∼ 20-30 eV) over the entire emission spectrum (from 150 Å to 2000 Å).