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Title: Experimental measurements and noise analysis of a cryogenic radiometer

A cryogenic radiometer device, intended for use as part of an electrical-substitution radiometer, was measured at low temperature. The device consists of a receiver cavity mechanically and thermally connected to a temperature-controlled stage through a thin-walled polyimide tube which serves as a weak thermal link. With the temperature difference between the receiver and the stage measured in millikelvin and the electrical power measured in picowatts, the measured responsivity was 4700 K/mW and the measured thermal time constant was 14 s at a stage temperature of 1.885 K. Noise analysis in terms of Noise Equivalent Power (NEP) was used to quantify the various fundamental and technical noise contributions, including phonon noise and Johnson-Nyquist noise. The noise analysis clarifies the path toward a cryogenic radiometer with a noise floor limited by fundamental phonon noise, where the magnitude of the phonon NEP is 6.5 fW/√(Hz) for the measured experimental parameters.
Authors:
; ; ; ;  [1]
  1. National Institute of Standards and Technology (NIST), 100 Bureau Drive, Gaithersburg, Maryland 20899 (United States)
Publication Date:
OSTI Identifier:
22308833
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 85; Journal Issue: 7; Other Information: (c) 2014 U.S. Government; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CAVITY RECEIVERS; CRYOGENICS; PHONONS; RADIOMETERS; TEMPERATURE MEASUREMENT; TEMPERATURE NOISE; TEMPERATURE RANGE 0065-0273 K