The Photometric Properties of Microwave High Intensity Discharge (HID) Lamps

Abstract

This paper calculates the visible radiations of discharges sustained by a microwave (mw) electromagnetic field of a high intensity discharge (HID) lamp. A microwave Mercury (Hg) lamp is considered to be excited by microwave electromagnetic fields in a cylindrical TM₀₁₀ mode. A 2.45 GHz microwave generator is going to be used to sustain a stable plasma column with discharge gases. A numerical model is used to obtain the power balance in the discharge based on a solution to the Elenbaas–Heller equation for the gas temperature, and a simple “skin depth” model to describe the penetration of the maintenance electric field in the discharge. The obtained plasma for the discharge is assumed to be at local thermodynamic equilibrium (LTE) with no diffusion. Classical spectral line broadening theory is used to provide information on the visible spectrum. However, this theory is inadequate to describe the UV and IR portion of the spectrum, so self-consistent modeling of these discharges is not possible at present and only visible radiations are considered. We show in this work that an increase in electric power does not necessarily lead to an increase in the visible radiation of mw HID lamp. The photometric curve of a pure Hg mw lamp is also calculated. The lamp volume is subdivided into meshes and a local absorption and emission coefficients is assigned to each mesh. A model based on ray tracing method is employed to simulate the radiation transport in these lamps. The line profile is obtained by the convolution of the Lorentzian and Quasi-static profiles. The output flux, luminous flux, luminous efficacy, the Correlated Color Temperature (CCT) and photometric curves of the lamp are therefore obtained.