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.
The Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD) is a space mission to search for and characterize the signature of inflation in the polarized signal from the cosmic microwave background (CMB), and probe fundamental physics. LiteBIRD will precisely measure the polarization of the cosmic microwave background on large angular scales ≳ 1 deg. It will survey the full sky with three telescopes covering 15 frequency bands centered at frequencies from 40 to 402 GHz. The pixel design for the low- and mid-frequency telescopes features a hemispherical lenslet coupled to a broadband sinuous antenna. The radiation detected by the sinuous antenna propagates through a superconducting microstrip and on-chip bandpass filters before being detected by superconducting transition edge sensor (TES) bolometers. The TES design fulfills requirements for low saturation power of the space environment while maintaining a fast time response for use with a continuously-rotating half-wave plate. We present measurements of the electrical and thermal properties of the TES detectors with values required for the LiteBIRD mission, the design and measurements of a dual-polarization trichroic pixel at 40, 60, and 78 GHz suitable for the low-frequency telescope, and the design and preliminary measurements for a detector array at 100, 140, and 195 GHz suitable for the mid-frequency telescope.
LiteBIRD is a JAXA-led strategic large-class satellite mission designed to measure the polarization of the cosmic microwave background and Galactic foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020s. The scientific payload includes three telescopes which are called the low-, mid-, and high-frequency telescopes each with their own receiver that covers a portion of the mission’s frequency range. The low frequency telescope will map synchrotron radiation from the Galactic foreground and the cosmic microwave background. We discuss the design, fabrication, and characterization of the low-frequency focal plane modules for low-frequency telescope, which has a total bandwidth ranging from 34 to 161 GHz. There will be a total of 4 different pixel types with 8 overlapping bands to cover the full frequency range. These modules are housed in a single low-frequency focal plane unit which provides thermal isolation, mechanical support, and radiative baffling for the detectors. The module design implements multi-chroic lenslet-coupled sinuous antenna arrays coupled to transition edge sensor bolometers read out with frequency-domain mulitplexing. While this technology has strong heritage in ground-based cosmic microwave background experiments, the broad frequency coverage, low optical loading conditions, and the high cosmic ray background of the space environment require further development of this technology to be suitable for LiteBIRD. In these proceedings, we discuss the optical and bolometeric characterization of a triplexing prototype pixel with bands centered on 78, 100, and 140 GHz.
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.
LiteBIRD is a JAXA-led strategic Large-Class satellite mission designed to measure the polarization of the cosmic microwave background and cosmic foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020's. The primary focus of the mission is to measure primordially generated B-mode polarization at large angular scales. Beyond its primary scientific objective LiteBIRD will generate a data-set capable of probing a number of scientific inquiries including the sum of neutrino masses. The primary responsibility of United States will be to fabricate the three flight model focal plane units for the mission. The design and fabrication of these focal plane units is driven by heritage from ground based experiments and will include both lenslet-coupled sinuous antenna pixels and horn-coupled orthomode transducer pixels. The experiment will have three optical telescopes called the low frequency telescope, mid frequency telescope, and high frequency telescope each of which covers a portion of the mission's frequency range. JAXA is responsible for the construction of the low frequency telescope and the European Consortium is responsible for the mid- and high- frequency telescopes. The broad frequency coverage and low optical loading conditions, made possible by the space environment, require development and adaptation of detector technology recently deployed by other cosmic microwave background experiments. This design, fabrication, and characterization will take place at UC Berkeley, NIST, Stanford, and Colorado University, Boulder. We present the current status of the US deliverables to the LiteBIRD mission.
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.
The Simons Observatory (SO) will perform ground-based observations of the cosmic microwave background (CMB) with several small and large aperture telescopes, each outfitted with thousands to tens of thousands of superconducting aluminum manganese (AlMn) transition-edge sensor bolometers (TESs). In-situ characterization of TES responsivities and effective time constants will be required multiple times each observing-day for calibrating time-streams during CMB map-making. Effective time constants are typically estimated in the field by briefly applying small amplitude square-waves on top of the TES DC biases, and fitting exponential decays in the bolometer response. These so-called “bias step" measurements can be rapidly implemented across entire arrays and therefore are attractive because they take up little observing time. However, individual detector complex impedance measurements, while too slow to implement during observations, can provide a fuller picture of the TES model and a better understanding of its temporal response. Here, we present the results of dark TES characterization of many prototype SO bolometers and compare the effective thermal time constants measured via bias steps to those derived from complex impedance data.
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