Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Experimental measurements and noise analysis of a cryogenic radiometer



Solomon I. Woods, Timothy M. Jung, Adriaan C. Carter, Raju V. Datla , Stephen M. Carr


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 diff erence 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 clarifi es 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^0.5) for the measured experimental parameters.
Review of Scientific Instruments


bolometers, cryogenic detectors, radiometers, metrology, standards and calibration
Created July 10, 2014, Updated February 19, 2017