Reduction of the background thermal radiation input to a cryogenic radiometer for the measurement of a spectrally filtered continuum source

摘要

An optical system is proposed that reduces the background thermal radiation input to a cryogenic radiometer by a factor of almost 40000. This system is based on a concave grating which can be configured to create a scanning monochromator with the cryogenic radiometer entrance aperture as the exit slit. A cryogenic radiometer is described that has a sensitivity of 1 pW and which is suitable for use with this monochromator and a continuum source to calibrate detectors at an uncertainty level of one part in 10~(5).