Infrared detector spectral responsivity calibration facility at the National Institute of Standards and Technology (NIST)

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The National Institute of Standards and Technology (NIST) is developing a facility to provide absolute responsivity calibrations of detectors in the 2 to 20 micrometers spectral region. The goal is to tie the measurements of NIST's primary radiometric scale with a 1 (sigma) uncertainty of approximately 5%. The system uses chopped thermal IR sources, a room temperature prism/grating spectrometer for spectral selectivity with 1 - 2% spectral resolution and a cryogenic bolometer as a transfer standard detector. The composite design bolometer has an absorbing surface 5 mm in diameter, a nonlinearity &lt; 1% over 5 decades and a responsivity of approximately 1 X 10<SUP>4</SUP> V/W without amplification. This bolometer is being calibrated against the High Accuracy Cryogenic Radiometer, the nation's primary standard for optical radiometric measurements. The bolometer's spectral response will also be measured using the Low Background Infrared facility at NIST, the nation's primary blackbody calibration facility.