ISSTT Proceedings

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A Broadband THz Receiver for Low Background Space Applications

Authors:
C. Hagmann, D.J. Benford, A.C. Clapp, P.L. Richards, P. Timbie
Abstract:
We have developed a sensitive bolometric receiver for low background space applications. In a 10 % bandwidth at 1 THz, this receiver is approximately 100 times more sensitive than a quantum limited heterodyne receiver with a 1 GHz IF bandwidth. This receiver is designed to be used for the long wavelength band (200-700 µm) in the MIPS instrument on NASA's SIRTF satellite. The bolometers are cooled to 100 mK by an adiabatic demagnetization refrigerator. Roughly 60 g of cesium chrome alum salt is partially demagnetized to 100 mK, followed by a slow regulated downramp to compensate for the heat leak. The hold time of the ADR system is about 18 hours with a temperature stability of [Delta]Trms [approx.] 10 µK. The composite bolometers have electrical reponsivities of 10 9 V/W and electrical NEP's of about 3×10-17 W/[square root]Hz. The bolometer signals are read out by JFET preamplifiers located on the helium plate and operated at 120 K. We have addressed a number of space qualification issues, such as the development of an analog magnet controller, construction of a cryogenic shake-table for bolometers and selection of the paramagnetic salt CCA which can survive a bakeout at 50 °C. The receiver is scheduled to be flown in the spring of 1992 on a balloon telescope. This flight has a dual purpose. One is to provide a realistic test of the capabilities of the new receiver. The other is to search for anisotropies in the cosmic microwave background on scales of a few degrees.
Categories:
Detectors, Mixers
Year:
1992
Session:
13
Full-text:
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Page Number(s):
678-687