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Proceedings Paper

Terahertz calorimetry: an absolute power meter for terahertz radiation and the absorptivity of the Herschel Space Observatory telescope mirror coating
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Paper Abstract

A new calorimetric absolute power meter has been developed for THz radiation. This broad band THz power meter measures average power at ambient temperature and pressure, does not use a window, and is insensitive to polarization and time structure of THz radiation. The operation of the power meter is based on the calorimetric method: in order to determine the power of a beam of THz radiation, the beam is used to illuminate a highly absorbing surface with known BRDF characteristics until a stable temperature is reached. The power in the incident beam can then be determined by measuring the electric power needed to cause the sample temperature rise. The new power meter was used with laser calorimetry to measure the absorptivity, and thus the emissivity, of aluminum-coated silicon carbide mirror samples produced during the coating qualification run of the Herschel Space Observatory telescope to be launched by the European Space Agency in 2007. The samples were measured at 77 Kelvin to simulate the operating temperature of the telescope in its planned orbit around the second Lagrangian point, L2, of the Earth-Sun system. The absorptivity of both clean and dust-contaminated samples was measured at 70, 118, 184 and 496 mm and found to be in the range 0.2 - 0.8%.

Paper Details

Date Published: 8 April 2004
PDF: 9 pages
Proc. SPIE 5354, Terahertz and Gigahertz Electronics and Photonics III, (8 April 2004); doi: 10.1117/12.526994
Show Author Affiliations
Tjeerd O. Klaassen, Technische Univ. Delft (Netherlands)
J. Niels Hovenier, Technische Univ. Delft (Netherlands)
Jacqueline Fischer, Naval Research Lab. (United States)
Gerd Jakob, Max-Planck-Institut fuer extraterrestrische Physik (Germany)
Albrecht Poglitsch, Max-Planck-Institut fuer extraterrestrische Physik (Germany)
Oren Sternberg, Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 5354:
Terahertz and Gigahertz Electronics and Photonics III
R. Jennifer Hwu, Editor(s)

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