Deuterium Lamps as Transfer Standards for Spectral Radiance Measurements

摘要

This report describes the work carried out at NPL and PTB to improve the performance of a low pressure deuterium discharge lamp, so that it can be used as a transfer standard in the spectral range 120 to 350 nm. To this end it was necessary: to replace the original quartz windows by magnesium fluoride single crystal plates, which were cut perpendicular to the c-axis of the crystal and which had to be free of impurities, to construct the lamps in that way that the directional uniformity of the emitted radiation is within the demands, to age the lamps and to preselect only those of which the irradiance was stable within +- 1% during a thirty minute period after warm-up, to improve the commercially available electrical power supply to meet the operational needs of the lamps. Thus, the deuterium lamps drifted by about 3% over a period of 100 h at all wavelengths except at 250 nm, where the ageing increased to 4.5%. A liquid nitrogen trap has been developed which can be installed between the vacuum system and the lamp. This reduced to about 2% the decrease of the window's transmission during the first hour of operation, caused by the deposition of oil from the vacuum system. (ERA citation 12:048279)