METAL HALIDE LAMP WITH TRACE T1I FILLING FOR IMPROVED DIMMING PROPERTIES

An arc discharge metal halide lamp for use in selected lighting fixtures having a discharge chamber with light permeable ceramic walls about a discharge region. A pair of electrodes are supported in the discharge region spaced apart from one another. Ionizable materials are provided in the discharge region comprising mercury, a noble gas, and at least two metal halides including a magnesium halide and a sodium halide, a rare earth element, and thallium iodide in a molar quantity which is between 0.7 and 5% of that total molar quantity of all halides present in the discharge chamber.