NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Active Cavity Radiometer Based on High-TC Superconductors
Published
Author(s)
Joseph P. Rice, Raju V. Datla, Leila R. Vale, David A. Rudman, M L. Sing, D Robbes
Abstract
To implement the detector-based radiometric scale in the new Medium Background infrared [MBIR] facility at the National Institute of Standards and Technology [NIST], we have developed an electrical substitution cavity radiometer that can be operated at liquid nitrogen temperature. This MBIR Active Cavity Radiometer [ACR] utilizes a temperature-controlled receiver cone and an independently temperature-controlled heat sink. Being a thermal-type detector, low noise and drift of the radiometer signal depends mainly on low-noise temperature control of the receiver and heat sink. Using high critical-temperature [Tc] superconducting thin film temperature sensors in the active control loops, we have achieved closed-loop temperature controllability of better than 10 K at 89 K for a receiver having an open-loop thermal time constant of about 75 seconds. For a flux level of 1 υW to 10 υW, the rms noise floor over a measurement cycle time is below 20 nW. This is the lowest noise level yet reported for a liquid nitrogen cooled electrical-substitution radiometer and it is the first demonstration of the use of high-Tc superconductors in such a radiometer. Potential uses for this ACR in the MBIR facility include absolute measurement of the broadband radiance of large-area 300 K cryogenic blackbody sources, and absolute measurement of the spectral radiance of laser-illuminated integrating spheres for improved relative spectral responsivity measurements of infrared transfer standard radiometers.
Rice, J.
, Datla, R.
, Vale, L.
, Rudman, D.
, Sing, M.
and Robbes, D.
(1998),
Active Cavity Radiometer Based on High-TC Superconductors, NEWRAD
(Accessed October 4, 2025)