This invention relates to a thermoluminescent phosphor for the measurement of low radiation doses, including calcium sulphate (CaSO.sub.4), Dysprosium (Dy) and manganese (Mn), wherein Dy and Mn are present as dopants. A process for the preparation of a thermoluminescent phosphor is also provided. The process includes the steps of: separately dissolving calcium sulphate (CaSO4), Dysprosium chloride (DyCh) and Manganese chloride (MnC) in hot concentrated sulphuric acid, to obtain sulphuric acid solutions of CaSO4, DyCb and MnCb; mixing the solutions; and followed by slow evaporation of the solvent to obtain a powder of microcrystalline phosphor of CaSO4:Dy, Mn.

An electrodeless lamp driven by a microwave generator is disclosed. The electrodeless lamp includes a first infill composed of mercury-free metal halide and provides a continuous full spectrum radiation including ultraviolet ray, visible light, and infrared ray. Thereby, the electrodeless lamp, which meets the standard of AM 1.5 G, has advantages of environmental friendliness, high efficacy lighting, long service life, and low light decay, and therefore, have become applicable in the field of solar simulators.