Spatio-temporal study of the deviations from thermal equilibrium in a high-pressure mercury plasma working under an ac power supply

This work deals with the study of deviations from thermal equilibrium in hi gh-pressure mercury discharges operating in ac mode. A one-dimensional time -dependent fluid model assuming a non-equilibrium plasma (two-temperature c ode) has been developed. This code solves, self-consistently, the set of hy drodynamic equations describing the discharge plasma, coupled with an equat ion describing the power supply circuit. This code is based on a finite-ele ment method and it has been optimized in order to keep CPU times realistic. Our calculations at an industrial 50 Hz frequency, validated by using exper imental data from the literature, allow us the possibility to better unders tand the mechanisms that are responsible for deviations from thermal equili brium within an ac cycle. Furthermore, a parametric study allows us to stud y in detail the influence of some key parameters, such as frequency and mer cury load on those deviations.