Publicado 12 números por año
ISSN Imprimir: 0040-2508
ISSN En Línea: 1943-6009
Indexed in
Absolute Cryogenic Receiver as a Reference Laser Radiation Sensor
SINOPSIS
The problem of accurate and reliable measurement of the power of optical radiation, including laser radiation, is a problem of great current interest. Considerable progress has been made over the last decades in the development of electrically calibrated thermal optical receivers. Having in mind the importance of this problem, the International Lighting Commission (ILC) published the official report "Electrically Calibrated Thermal Optical Radiation Receivers" (absolute radiometers [1]), in which issues related to the development of methods for electrically controlled thermal substitution as well as techniques for estimating the contributing errors caused by nonequivalent substitution are considered.
The classical configuration of a thermal optical radiation receiver is a blackened absorbing cavity whose outer surface supports the heating coil of an electrical substitution circuit. Optimal radiometers operated at room temperature demonstrate measurement accuracy of the order of 0.1% [2]. In order to further improve the accuracy, new approaches were considered which resulted in the development of a cryogenic absolute radiometer [3]. A thermal cavity receiver was used as a basic construction. In order to radically improve its characteristics, the receiver was placed in a helium cryostat. At liquid-helium temperatures the radiation and thermal conductance losses are dramatically reduced, which makes it possible to construct a receiver with implemented heat sink. Besides, due to the fact that the thermal capacity of copper was dramatically reduced, the sensitivity of the radiometer was significantly improved. The investigation shows that the radiation power measurement accuracy for such a radiometer is as high as 0.01%.
In this paper we consider the design and basic technical characteristics of electrically compensated cryogenic thermal optical radiation receivers. The device uses the operating principle of a continuous-flow calorimeter with implemented heat sink. The receiving cavity is configured as a thin-walled copper case with a blackened inner surface. Two heating coils are mounted on the outer surface. The supply wires are made from a superconducting titanium-niobium alloy. The heating of the cavity is controlled by a semiconductor temperature-to-voltage converter.