Aarhus University intends to buy a Light Flash Apparatus (LFA) for research. The LFA will be used for measurement of thermal diffusivity and conductivity of various scientific samples at elevated temperatures. The samples are of limited size, typically discs or squares with a size of 10 or 12.7 mm. Of special importance are very thin samples of single crystals. For these samples we expect a half time for the temperature rise after applying the light pulse of 10-50 microseconds and in some cases even less. We thus require an apparatus able to supply short light pulses of no more than 10 microseconds.