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17 February 2003 1.8 THz superconductive hot-electron bolometer mixer for Herschel
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We are developing terahertz mixers to cover the highest frequency band ("6H") for the heterodyne instrument (HIFI) aboard the Herschel Space Observatory. The mixer will be optimized for operation at 1.8 THz, with an input bandwidth of at least 0.2 THz. Some of the key spectroscopic lines in this frequency band are the fine-structure transition of ionized carbon at 1.9 THz, and numerous rotational transitions of water vapor and other hydrides. The mixers will employ a superconductive hot-electron bolometer as the mixing element, for which we will use a diffusion-cooled niobium microbridge. This variant allows an IF bandwidth that meets the range required for HIFI's 4-8 GHz IF. The mixer will be operated at ~2 K bath temperature. The sensitivity requirement is a double sideband mixer noise temperature of Tmix / ν ~ 1,000 K / THz , which has been previously demonstrated with this type of mixer. The mixer is a quasioptical design, employing a twin-slot planar antenna mounted on the backside of an elliptical silicon lens. Initial measurements indicate that that these mixers can be adequately pumped with a solid-state 1.5 THz local-oscillator source. HEB mixers are extremely delicate and susceptible to environmental damage; we have therefore focused a good deal of attention to engineering a rugged, flyable mixer.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jonathan Kawamura, Bruce Bumble, Dennis G. Harding, William R. McGrath, Paolo Focardi, and Rick LeDuc "1.8 THz superconductive hot-electron bolometer mixer for Herschel", Proc. SPIE 4855, Millimeter and Submillimeter Detectors for Astronomy, (17 February 2003);

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