Diplexers were developed to separate a wide intermediate frequency (IF) range and utilize IF below 4 GHz for wideband submillimeter array (wSMA) receivers. Diplexers were designed using superconducting materials and processed via in-house thin film fabrication. The diplexers were designed to operate around 4 K and can be integrated with other cryogenic components.
The far infrared instrument SAFARI spectrometer on board the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) provides moderate resolution spectra (R~300) with simultaneous coverage over 34 to 230 μm. With the high sensitivity TES detectors, the SAFARI can reach the sensitivity down to ~7×10-20 W/m2. In order to provide accurate calibration for the TES readout circuit, a calibration source assembly (CSA) is developed to provide a stable and absolute flux radiation to the spectrometer over the whole spectral range. The CSA has a primary function during observations to take periodic reference measurement to correct for drift, subtracting backgrounds, etc from the detector. The CSA is composed of three microlamps and one integrating sphere. The microlamps are made of resistance wires by microlithography to mimic square blackbody sources. By combining an 81K microlamp and a 24K microlamp, a reasonably flat spectrum can be produced at the output of the integrating sphere. The radiation to the transition edge sensor detector pixel is around 1×10-16 W. The integrating sphere can also provide a uniform output to cover the size of SAFARI field of view including the target and sky pixels. In this paper, the CSA design and the prototype results of the microlamp and the integrating sphere are presented.
We have fabricated new superconductor-insulator-superconductor (SIS) mixers chips for the 16-element Heterodyne Array Receiver Program (HARP) instrument on the James Clerk Maxwell Telescope (JCMT). The original spare mixer chips were limited and not performed as well as the used ones in HARP. The ability to manufacture new mixer chips would therefore be important for the repair and upgrade of HARP. Our immediate goal is to replace the current nonfunctional mixers in HARP with new chips. We modified the designs of waveguide probe and the matching circuit of the SIS mixer chip. The newly designed chips were fabricated with a quality factor (Rsg/Rn) over 10. The double-sideband (DSB) receiver noise temperature (Trx) is lower than 80K at frequencies between 325 GHz and 375 GHz, which is comparable to the best of the original devices. Three of the sixteen mixers have been replaced and they work very well.
Since the start of full science operations from 2004, the Submillimeter Array has been implementing plans to expand IF bandwidths and upgrade receivers and cryostats. Metal mesh low-pass filters were designed to block infrared (IR) radiation to reduce the thermal load on the cryostats. Filters were fabricated on a quartz wafer through photolithography and coated with anti-reflection (AR) material. The filters were tested from 200 to 400 GHz to verify their passband performances. The measurement results were found to be in good agreement with EM simulation results. They were tested in the far-infrared (FIR) frequency range to verify out-of-band rejection. The IR reflectivity was found to be approximately 70%, which corresponded to the percentage of the area blocked by metal.
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