Present State of the Determination of Thermodynamic Temperatures near the Freezing Point of Silver by Absolute Cryoradiometry

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Abstract
The paper describes a method for determination of thermodynamic temperatures by measurement of the irradiance of a black body. Silicon pn-photodiodes, calibrated against a cryogenic radiometer, are used for the absolute irradiance measurements. This method enables the establishment of a radiometrically based high temperature scale, i.e. it requires no reference temperature. Stability tests of the cryogenic radiometer system and results of photodiode calibrations are presented. The uncertainties of the method are discussed with special emphasis on diffraction effects and on the spectral properties of the interference filters used for wavelength selection.