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We are developing the frequency-domain multiplexing (FDM) readout for the SAFARI far-infrared spectrometer on board the SPICA space observatory. Each readout channel comprises a set of ~ 160 TESs and LC filters and is read out with a SQUID preamplifier. Baseband feedback is applied to overcome the dynamic range limitations of the SQUID. We have carried out extensive characterization of a test readout system coupled to a 176-pixel TES bolometer array in order to understand and optimize the system. We present our latest measurements of this 176-pixel FDM demonstrator, focusing on the noise contribution from the SQUID. [ABSTRACT FROM AUTHOR]

SCUBA-2, which replaces the Submillimetre Common User Bolometer Array (SCUBA) (Mon. Not. R. Astron. Soc. 303 (1999) 659) on the James Clerk Maxwell telescope in 2006, will be the first CCD-like array for submillimeter astronomy. Unlike previous detectors which have used discrete bolometers, SCUBA-2 has two DC-coupled, monolithic, filled arrays with a total of ∼10,000 bolometers. It will offer simultaneous imaging of an 8×8 arcmin field of view at wavelengths of 850 and 450 μm. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimetre interferometers such as ALMA. SCUBA-2''s absorber-coupled pixels use superconducting transition edge sensors (Ph.D. Thesis, Stanford, 1995) operating at ∼120 mK for photon noise limited performance. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes (Nucl. Instr. and Meth. A, these proceedings). Electrical connections are made through indium bump bonds to a backplane that incorporates a SQUID time-domain multiplexer. We describe the key technologies that make SCUBA-2 possible and give an update on the considerable progress in the detector development and instrument design that has taken place over the last 2 years. [Copyright &y& Elsevier]

Abstract: We describe progress in the development of a close-packed array of bolometers designed for use in photometric applications at millimeter wavelengths from ground-based telescopes. Each bolometer in the array will use a proximity-effect Transition Edge Sensor (TES) sensing element and each will have integrated Normal-Insulator-Superconductor (NIS) refrigerators to cool the bolometer below the thermal reservoir temperature. The NIS refrigerators and acoustic-phonon-mode-isolated bolometers are fabricated on silicon. The radiation absorbing element is mechanically suspended by four legs, whose dimensions are used to control and optimize the thermal conductance of the bolometer. Using the technology developed at NIST, we fabricate NIS refrigerators at the base of each of the suspension legs. The NIS refrigerators remove hot electrons by quantum-mechanical tunneling and are expected to cool the biased (10pW) bolometers to while the bolometers are inside a pumped 3He-cooled cryostat operating at . This significantly lower temperature at the bolometer allows the detectors to approach background-limited performance despite the simple cryogenic system. [Copyright &y& Elsevier]

We report on the design and construction of an 8×8 bolometer array designed to operate at 90 GHz on the new 100 m Green Bank Telescope (GBT). The bolometers are Transition Edge Superconducting (TES) detectors read out using a SQUID multiplexing system. The receiver will be one of the first astronomical instruments to use such detectors. To cool the detectors, we have developed 3He and 4He sorption refrigerators that cycle from a two-stage pulse-tube cryocooler. The system has been demonstrated to be robust, to be capable of cycling autonomously, and to provide 15 μW of cooling below 286 mK with a hold time over 70 h. Although modest in size, a combination of the size of GBT and the low noise of the TES detectors will make our receiver one of the most sensitive of its kind. [Copyright &y& Elsevier]