Diagnostics and characterization of nonequilibrium mercury plasma state in high-pressure lamps

Plasma diagnostics and characterization of the plasma state of equilibrium in high-pressure mercury discharges are of immediate interest in the design and optimization of new radiation sources. The temperatures and the species densities in mercury plasmas at 5 and 2 bar pressures operated at 50 Hz have been determined using an equilibrium-free method based on self-reversed lines. The results show that the actual plasma state differs strongly from the LTE state. At the maximum current phase the plasma is a two-temperature one, in ionizing phase, and on nonequilibrium excitation; the ground state is overpopulated whereas the plasma is underionized.