2022 Volume 106 Issue 1 Pages 55-68
We developed a simulation model to analyze the characteristics of low-pressure mercury-argon torus plasma generated in an inductive fluorescent lamp. This model is based on the classic models developed by Waymouth, Bitter and Cayless, and the characteristics of the torus plasma with non-circular cross-section can be evaluated by applying the concept of “equivalent tube” and “equivalent discharge”. We included the elastic collision of electrons with mercury atoms to take into account the low filling gas pressure of argon, i.e., ～20 Pa. The accommodation coefficients, which were originally introduced by Waymouth to fit the calculated results with experimental data, were reexamined, i.e., the ionization cross-section from 63P levels and the effective imprisonment time of the resonance radiation. The calculated plasma parameters, electrical characteristics, luminous flux and efficacy showed good agreement with the experimental data. This agreement mainly attributes to the accommodation coefficients we selected, and the physical interpretation of these coefficients was suggested. We applied the model to investigate the possibility of further improvement in the luminous efficacy by changing the shape of the discharge vessel, mercury vapor pressure, and argon gas pressure. The results indicate that the luminous efficacy is expected to increase up to about 7% with a larger vessel diameter, lower mercury vapor pressure, and lower argon gas pressure. Our model is expected to be useful in designing the driving circuit as well as addressing the thermal issue of an inductive fluorescent lamp.
