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The Low Background Infrared Calibration Facility (LBIR) at the National Institute of Standards and Technology has been in operation for calibration measurements of ihe radiant power emitted fn>rn infrared radiation (IR) sources, such as cryogenic blaclcbodies, for more than 2 years. The IR sources arc sent to NIST by Customers from industiy, government, and university laborato^ii^s. An absolute ciyngenic radiometer is used as the standard detector to measure the total radiant power at its aperture. The low background is provided by a closed cycle helium refrigeration system that maintains the inner parts of Ihe calibration chamber at 20 K. The radiance temper* ature of the blackbody is deduced from the measured power and cottipared with the htackbody temperature sensor data. The calibration procedures and data analysts arc illustrated using the measurements of a typical blackbody.

We report an international interlaboratory dual experiment to determine the calibration factor used to calculate the interstitial oxygen content of silicon from room‐temperature (300 K) infrared (IR) absorption measurements. We conducted round robins for both the infrared and the absolute measurements on the same or equivalent specimens. The calibration factor for computing the oxygen content of silicon in parts per million atomic (ppma) from a room‐temperature measurement of the absorption coefficient at 1107 cm−1 was determined to be 6.28±0.18 normalppma/cm−1 . The IR round robin showed a reproducibility on the order of 3%.

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