THE NPL REFERENCE SOURCES OF BLACKBODY RADIATION

The National Physical Laboratory (NPL) maintains a range of reference blackbody cavities of its own design with apertures from 3.0 to 100 mm in diameter for use over the temperature range 10-1064 degrees C. These sources are used for calibration of radiation thermometers and evaluation and calibration of industrial blackbody cavities over the wavelength range 0.9-14 mu m. This paper describes the design of the cavities and their intercomparison using a high-precision infrared radiometer. The results of the intercomparison showed a radiance temperature compatibility of better than +/- 0.6 degrees C over a wide temperature range and therefore validates the high quality of the NPL blackbody cavities as reference sources of thermal radiation.