An evaluation of the contribution of radiation diffusion to thermal conductivity in high-pressure discharge lamps from operating-voltage and wall-temperature measurements

The contribution of the radiation diffusion to the thermal conductivity in high-pressure discharge lamps is evaluated from operating-voltage and wall-temperature measurements for several cylindrical ceramic discharge tubes filled with mercury and argon as the rare gas. From calculations of using spectral line data of mercury, it is shown that the electrical conductivity can be well represented by a linear function of the heat-flux potential S . Under this assumption, the energy balance can be solved analytically and plasma parameters, i.e. radiation-diffusion and plasma-temperature profiles, can be calculated from the operating voltage and wall temperature without knowledge of spectral lines. The results are in good agreement with numerical calculations of the energy balance involving calculation of the radiation diffusion from spectral line data. The method may also be applied to other buffer gases for which there is a linear dependency of . This may be checked qualitatively by measurement of the temporal evolution of the operating voltage using the Cassie-Francis equation.