A New Standard of Spectral Irradiance

The National Bureau of Standards has made available a new standard of spectral irradiance in the form of a 200-W quartz-iodine lamp with a coiled-coil tungsten filament operating at about 3000°K and calibrated over the spectral range of 0.25 to 2.6 μ. The calibration of this standard is based upon the radiance of a blackbody as defined by the Planck law of radiation, since it was done by comparisons with the NBS standards of spectral radiance, of luminous intensity, and of total irradiance, each of which was established through the use of blackbodies. This standard is used without auxiliary optics. Because of its small physical size and high operating temperature, relatively high spectral irradiances may be obtained through its use.