High-frequency electrodeless discharges in helium

Modelling of high-frequency electrodeless discharges (HFEDs) in helium is presented. The model combines calculations of electromagnetic field profiles and plasma parameters including kinetics of the excited atomic states. A method of the self-consistent numerical solution for the plasma-field system is proposed. The method takes into account a temporal hierarchy of the kinetic processes in the HFED plasma. A stationary collision-radiative model for helium plasma is developed considering the following equations: (i) the transport equations for the electrons, (ii) the electron energy balance equation, (iii) the population rate equations for balance in the excited states and (iv) the electromagnetic field equations. Discharge properties are investigated in a numerical simulation. The electron density, electron temperature and absorbed power versus gas pressure and external magnetic field amplitude are obtained. The electromagnetic field profiles demonstrate a significant role of the skin effect. The intensities of the lines 587.6 and 728.1 nm are calculated, and are found to be in good agreement with the experimental data. The developed model is used to obtain optimal operation conditions of high-frequency electrodeless helium lamps.