Increasingly large arrays TES bolometers continue to be planned for future mm-wave observatories, but their scalability is limited by the associated cryogenic multiplexing readout. Microwave SQUID multiplexing is a natural candidate for future systems, as it already boasts a ~10x channel handling advantage over other readout schemes due to its large available bandwidth. By further doubling this bandwidth, the demonstration we present increases the multiplexing factor from the prior best of 910 to 1,820 and enables a simple 1:1 pairing of detector components and multiplexer hardware. We show a yield of greater than 80% based on TES IV curve quality and model typical nearest-neighbor crosstalk to be ~0.4%. Finally, we estimate from measurements that only 3% of the total noise budget would result from the multiplexer if installed in a typical sorption-cooled ground-based receiver observing 60 degrees above the horizon with a zenith precipitable water vapor of 1.3 mm.
The Simons Observatory is a new ground-based cosmic microwave background experiment, which is currently being commissioned in Chile’s Atacama Desert. During its survey, the observatory’s small aperture telescopes will map 10% of the sky in bands centered at frequencies ranging from 27 to 280 GHz to constrain cosmic inflation models, and its large aperture telescope will map 40% of the sky in the same bands to constrain cosmological parameters and use weak lensing to study large-scale structure. To achieve these science goals, the Simons Observatory is deploying these telescopes’ receivers with 60,000 state-of-the-art superconducting transition-edge sensor bolometers for its first five year survey. Reading out this unprecedented number of cryogenic sensors, however, required the development of a novel readout system. The SMuRF electronics were developed to enable high-density readout of superconducting sensors using cryogenic microwave SQUID multiplexing technology. The commissioning of the SMuRF systems at the Simons Observatory is the largest deployment to date of microwave multiplexing technology for transition-edge sensors. In this paper, we show that a significant fraction of the systems deployed so far to the Simons Observatory’s large aperture telescope meet baseline specifications for detector yield and readout noise in this early phase of commissioning.
Publisher’s Note: This paper, originally published on 22 December 2020, was replaced with a corrected/revised version on 12 March 2021. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.
AliCPT-1 is the first CMB degree scale polarimeter to be deployed to the Tibetan plateau at 5,250m asl. AliCPT-1 is a 95/150GHz 72cm aperture, two lens refracting telescope cooled down to 4K. Alumina lenses image the CMB on a 636mm wide focal plane. The modularized focal plane consists of dichroic polarization-sensitive Transition-Edge Sensors (TESes). Each module includes 1,704 optically active TESes fabricated on a 6in Silicon wafer. Each TES array is read out with a microwave multiplexing with a multiplexing factor up to 2,000. Such large factor has allowed to consider 10's of thousands of detectors in a practical way, enabling to design a receiver that can operate up to 19 TES arrays for a total of 32,300 TESes. AliCPT-1 leverages the technological advancements of AdvACT and BICEP-3. The cryostat receiver is currently under integration and testing. Here we present the AliCPT-1 receiver, underlying how the optimized design meets the experimental requirements.
The Simons Observatory is a suite of instruments sensitive to temperature and polarization of the cosmic microwave background. Five telescopes will host over 60,000 highly multiplexed transition edge sensor (TES) detectors. The universal focal plane modules (UFMs) package multichroic TES detectors with microwave multiplexing electronics compatible with all five receivers. The low-frequency arrays are lenslet-coupled sinuous antennas sensitive to 30 and 40 GHz. The mid-frequency and ultra-high-frequency UFMs are horn-coupled orthomode transducer arrays sensitive to 90/150 GHz and 225/280 GHz, respectively. Here we present the design, assembly details, and initial results of the first UFM.
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