Investigation on the feasibility of using an Ulbricht sphere for the absolute calibration of an ICP or other source at specific wavelengths
The short term and long term stability of an Ulbricht sphere was investigated by comparing its radiation at four Balmer wavelengths with those of two Sylvania projector lamps. A slight positive trend in the radiation intensity of the Ulbricht sphere was observed. This was attributed to a change in the molecular structure of the paint used to cover the inside of the sphere. However, the radiance varied less than 3% for 14 h burning time. The uncertainty in the primary calibration of the Tungsten standard lamp was given as ±3% in the wavelength range 400-600 nm. It was hence concluded that the sphere is suitable for spectral calibration purposes for a period of 14 h operational time without being recalibrated. © 1981.