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Comparison of Au and Pt Foils for an Imaging Bolometer

Byron J. PETERSON, Evgeny A. DRAPIKO, Dongcheol SEO¹⁾ and Naoko ASHIKAWA

National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292, Japan

1)

National Fusion Research Institute, Daejeon 305-806, Republic of Korea

(Received 19 March 2010 / Accepted 16 July 2010 / Published 1 October 2010)

Abstract

In the imaging bolometer a thin metal foil converts plasma radiated power to infrared radiation measured by an infrared camera. Calibration of the foil provides information on its sensitivity, which is helpful in selecting the best foil material. In this study thermal properties of submicron Au and Pt foils are investigated by heating the foils with a chopped HeNe laser beam (∼20 mW) and observing the temperature change, ΔT, and thermal time constant, τ, of the foil temperature. Assuming that the foil cooling is dominated by diffusion, we can compare the relative sensitivities of the foils by comparing the ratio of the thermal diffusivity to the thermal conductivity of the foil, κ/k, to the ratio ΔT/τ. The results indicate that Pt is more than 9 times more sensitive than Au even though standard thermal properties indicate that Au should be slightly (14%) more sensitive than Pt. This inconsistency indicates that the IR radiation is dominant over diffusion in the foil cooling. In that case the sensitivity should be evaluated by 1/k ∼ ΔT, which indicates that Pt is 8 times more sensitive than Au, while the ratio of thermal conductivities indicates that it should be only 4 times more sensitive.

Copyright (c) 2010 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

bolometer, plasma diagnostics, infrared radiation, imaging diagnostics, calibration

DOI: 10.1585/pfr.5.035

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This paper may be cited as follows:

Byron J. PETERSON, Evgeny A. DRAPIKO, Dongcheol SEO and Naoko ASHIKAWA, Plasma Fusion Res. 5, 035 (2010).