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Анализ работы пассивного лучеводного спектрометра с охлаждаемым селективным приёмником
The procedure of measurements and the formulas for calculating the sample's reflection (R) and transmission (T) coefficients with the use of a passive terahertz spectrometer are presented. The passive spectrometer comprises of cold and room-temperature chambers interconnected via a multimode waveguide (light pipe). Spectral selective liquid helium-cooled detector is placed at the cold side, and a specular disk shutter is positioned near the room-temperature end of the light pipe. The metered coefficients R and T can be calculated as a result of the two consecutive synchronous detection measurements — with the specimen placed before and after the shutter. Passive terahertz spectrometry based on the selective cooled detectors is a good alternative to active one when the use of a sophisticated teraherz radiation source is difficult or undesirable.