A medium temperature radiation calibration facility using a new design of heatpipe blackbody as a standard source

Abstract

A blackbody calibration facility which can cover the medium temperature range from 500 to 1200 K has been established. To cover the range from 500 to 800 K, a new design of heatpipe blackbody source which uses a mixture of caesium, potassium and sodium as the working fluid has been developed. The upper limit of the operating range of this heatpipe is around 1000 K. The temperature uniformity of the blackbody cavity over two thirds of its length from the closed end is better than 0.05% of the operating temperature (in kelvins). For the range from 800 to 1200 K, another heatpipe blackbody whose working fluid is sodium was manufactured. The temperature uniformity of the blackbody cavity in this device is 0.04% of the operating temperature. The calibration facility consists of a large turntable on which the reference and test blackbodies are positioned and a measurement guide on which an accurate radiometer is mounted. The measurement procedure yields an uncertainty of 0.4% (2σ ) in the calibration of industrial blackbodies.