18 August 2005 Stability characteristics of 1000 watt FEL-type QTH lamps during the seasoning and screening process
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Abstract
The National Institute of Standards and Technology (NIST) employ the 1000 watt FEL-type quartz-tungsten-halogen (QTH) lamp as its transfer device for the spectral irradiance scale. The cost of the calibrated lamps from the NIST makes it prohibitive to use them for routine calibrations. To dilute the costs and extend the working lifetime of the lamps it is customary to transfer the NIST scale to secondary lamps and then using these to transfer to tertiary (working standards) lamps. NOAA's Central UV Calibration Facility (CUCF) currently owns six of the NIST primary standards of spectral irradiance. The CUCF transfers the spectral irradiance scale from the NIST primaries to secondary standards, which in this case are also used as working standards. Careful seasoning and screening of the secondary lamps is essential to achieve the maximum benefit out of this transfer and the operation of the expensive primary standards. The process of lamp seasoning and screening techniques used by the CUCF is described here. They include visual inspection of the lamp envelope, filament and lead wires during each step of the screening process. Also, the temporal stability of the lamp irradiance, lamp current and voltage and anomalous emission and absorption lines is discussed. Some of the problems that the CUCF has found with lamps are also shown.
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Patrick Disterhoft, Patrick Disterhoft, } "Stability characteristics of 1000 watt FEL-type QTH lamps during the seasoning and screening process", Proc. SPIE 5886, Ultraviolet Ground- and Space-based Measurements, Models, and Effects V, 58860G (18 August 2005); doi: 10.1117/12.614584; https://doi.org/10.1117/12.614584
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