Evaluation of spectral irradiance transfer standards

The performance of spectral irradiance transfer-standard lamps has long bee n a concern in the radiometry and photometry communities. The adoption of a modified FEL-type lamp has recently been proposed as the most suitable tra nsfer standard for spectral irradiance measurements. While data have been p ublished on the performance of these lamps when operated continuously and i n a laboratory environment, however, little information is available on the ir performance under typical usage. The results are presented of "real-life " testing of over thirty FEL lamps both pre-selected, according to publishe d procedures, and direct from the manufacturer. When operated vertically al l of the lamps tested suffered terminal coil collapse after between 140 h a nd 250 h burn time. The reproducibility of the FEL lamps after transportati on is also investigated.