A new FEL-type quartz-halogen lamp as an improved standard of spectral irradiance

Based on extensive investigations of almost 100 high-power quartz-halogen l amps covering thirteen different types, seven different manufacturers and d ifferent batches with a total operating time of about 27 000 h, a new type of lamp (1000 W T6 modified FEL-type lamp, Osram Sylvania Inc.) has been se lected and its operating conditions have been optimized. This lamp, which a fter seasoning is about ten times more stable than the best lamps used befo re, is recommended as a reference and transfer standard of spectral irradia nce in the whole range between 250 nm and 3 mu m. While excellent short-ter m and long-term stability over operating times of several hundreds of hours can be achieved, the disadvantages of the new standard lamp lie in a long seasoning time (80 h to 100 h) and a noticeable sensitivity of the seasoned lamps to shock and vibrations. Typical results of the characterization, ca libration and reproducibility of the new standard lamp are presented and di scussed in order to illustrate its performance and to demonstrate how to us e it under optimal operation conditions.