Experimental research of energy balance during the formation of high energy plasma objects (EPO)

Abstract

High power microwave discharges in S2 vapour at pressures of several bars have been discovered as a highly eficient white light source several years ago [l]. The discharge spectrum is originating mainly from bound-bound transitions in the S2 B 3Cu--X 3Cg-band system. At such high S2 pressures re-absorption is an essential mechanism shifting the spectral maximum from the UV into the visible region [ 2 ] .Assuming spherical symmetry, local thermal equilibrium and a cubic temperature profile the onedimensional radiation transport equation is solved for each of the 330 vibronic bands connecting the niveaus v' = 0...9 and v" = 0...32 yielding a quantitative description of the spectrum with only two free parameters: the maximum discharge temperature T,, and the mean width 8vvib of a vibronic band. The response of the spectrum to variations of experimental conditions (Sz pressure, input power, ... ) may be expressed by very reasonable changes of these model parameters: The input power determines the total amount of radiation (via the value of Tmm) and the S2 pressure influences the position of the spectral maximum (reflected by the value of 8vyib). In the red and IR the experimental spectrum is higher than the simulation indicating contributions of continuum radiation or other molecular transitions which are not included in the model.