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Proceedings Paper

Picowatt infrared power measurement using an absolute cryogenic radiometer
Author(s): S. M. Carr; S. I. Woods; T. M. Jung; A.. C. Carter; R. U. Datla
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Paper Abstract

We report on initial measurements of the low-temperature thermal properties of a device that is similar to the experimental apparatus used for absolute cryogenic radiometry (ACR) within the Low Background Infrared Radiometry (LBIR) facility at NIST. 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. In order to evaluate the functionality of the device for use in a cryogenic radiometer, we measured the thermal resistance and thermal time constant of the system within the temperature range of 1.8 - 4.4 K. The measured thermal resistance and thermal time constant at 1.883 K were 2400 ± 500 (K/mW) and 24 ± 6 (s). This value for the thermal resistance should result in about an order-of-magnitude increase in radiometer sensitivity compared with the present ACR within LBIR. Although the sensitivity should increase by about an order-of-magnitude, the measured time constant is nearly unchanged with respect to previous ACRs within LBIR, due to the reduced dimensions of the receiver cavity. Finally, the thermal conductivity inferred from the measured thermal resistance and geometrical parameters was computed, with an average value of 0.015 (W/m-K), and compared with other measurements of polyimide from the literature.

Paper Details

Date Published: 7 May 2009
PDF: 8 pages
Proc. SPIE 7298, Infrared Technology and Applications XXXV, 72983Y (7 May 2009); doi: 10.1117/12.820290
Show Author Affiliations
S. M. Carr, National Institute of Standards and Technology (United States)
S. I. Woods, National Institute of Standards and Technology (United States)
T. M. Jung, National Institute of Standards and Technology (United States)
A.. C. Carter, National Institute of Standards and Technology (United States)
R. U. Datla, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 7298:
Infrared Technology and Applications XXXV
Bjørn F. Andresen; Gabor F. Fulop; Paul R. Norton, Editor(s)

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