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The Transition-Edge Sensor (TES) is an extremely sensitive device which is used to measure the energy of individual X-ray photons. For astronomical spectrometry applications, SRON develops a Frequency Domain Multiplexing (FDM) read-out system for kilopixel arrays of such TESs. Each TES is voltage biased at a specific frequency in the range 1 to 5 MHz. Isolation between the individual pixels is obtained through very narrow-band (high-Q) lithographic LC resonators. To prevent energy resolution degradation due to intermodulation line noise, the bias frequencies are distributed on a regular grid. The requirements on the accuracy of the LC resonance frequency are very high. The deviation of the resonance frequencies due to production tolerances is significant with respect to the bandwidth, and a controller is necessary to compensate for the LC series impedance. We present two such controllers: a simple orthogonal proportional-integrating (PI) controller and a more complex impedance estimator. Both controllers operate in baseband and try to make the TES current in-phase with the bias voltage, effectively operating as phase-locked loops (PLL). They allow off-LC-resonance operation of the TES pixels, while preserving TES thermal response and energy resolution. Extensive experimental results -- published in a companion paper recently -- with the proposed methods, show that these controllers allow the preservation of single pixel energy resolution in multiplexed operation.

The next-generation instruments for millimeter-wave astronomy will require large arrays of detectors to surpass current performance [see (Hui, 2016) and (Ade, 2018)]. On account of integration challenges, focal planes relying on transition edge sensor (TES) bolometers will not scale gracefully. Thermal Kinetic Inductance Detectors (TKIDs) are highly scalable and have the design flexibility to solve this problem. We present an update on our detector development and systems engineering in preparation for a 2022 TKIDs camera deployment that includes noise performance, optical characterization, and a calibration strategy.

SPT-3G is a polarization-sensitive receiver, installed on the South Pole Telescope, that measures the anisotropy of the cosmic microwave background (CMB) from degree to arcminute scales. The receiver consists of ten 150~mm-diameter detector wafers, containing a total of 16,000 transition-edge sensor (TES) bolometers observing at 95, 150, and 220 GHz. During the 2018-2019 austral summer, one of these detector wafers was replaced by a new wafer fabricated with Al-Mn TESs instead of the Ti/Au design originally deployed for SPT-3G. We present the results of in-lab characterization and on-sky performance of this Al-Mn wafer, including electrical and thermal properties, optical efficiency measurements, and noise-equivalent temperature. In addition, we discuss and account for several calibration-related systematic errors that affect measurements made using frequency-domain multiplexing readout electronics., Comment: 9 pages, 5 figures, submitted to the Journal of Low Temperature Physics: LTD18 Special Edition

We have developed a new transition-edge sensor material with critical temperature (Tc) in the range 100–200 mK. The new material is a solid solution of two superconducting components, MoxNb1−x, co-sputtered from two high-purity single-component targets (Mo and Nb). The Tc has a minimum (dTc/dx = 0) at an intermediate concentration of the components. We have optimized the deposition parameters and composition to provide films with a sharp superconducting transition at ~ 150 mK. We investigated structural features of the films and surface morphology using X-ray diffraction (XRD) and scanning electron microscopy. The XRD measurements indicate that the grown films are polycrystalline, with a preferred orientation along the (110) crystal direction and a clear correlation between superconducting properties and film microstructure.

We developed a Ti/Au bilayer optical superconducting transition edge sensor (TES) laying on an optical fiber self-aligned structure. The bilayer approach enables us to control the superconducting transition temperature T C , which results in 8-μm-square-sized TES with T C as high as 314.0 mK. Moreover, the TES device is micro-machined so that it can be easily assembled with an optical fiber via a self-aligned method. Our TES device achieved a system photon detection efficiency (PDE) of 83.6% at 940 nm with an energy resolution of 0.21 eV. Electrical and effective time constants (rise time and decay time) were as short as 74 and 75 ns, respectively. We also theoretically analyzed the imperfect system PDE. According to this analysis, the imperfection originated mainly from misalignment between the TES and the optical fiber, and the system PDE will be increased up to >95% by use of an optical fiber with a smaller mode field diameter.

The successful realization and broad deployment of transition edge sensor (TES)-based detector systems has led to significant demand for time-division and code-division superconducting quantum interference device (SQUID) multiplexers time division multiplexing (TDM) and code division multiplexing (CDM) as essential components of the cryogenic readout chain. TDM and CDM circuits are produced by the Boulder Microfabrication Facility in large quantities and in multiple varieties to meet the needs of various bolometric and calorimetric applications. In most cases, the basic functionality of these devices must be verified before they are passed along to internal or external collaborators for integration into scientific instruments. We have developed a test bed that utilizes the NIST TDM/CDM read-out electronics to make automated multiplexed measurements on sixteen devices simultaneously in a 4 K liquid-helium dip probe. The optimization of the measurement process has resulted in vastly improved throughput and enhanced data products. We present a thorough analysis of results from the application of the test process to flux-activated-switch-style multiplexers. The utility of this approach in identifying fabrication trends, yield indicators, and common failure modes will be demonstrated.

Next-generation focal planes comprising dozens of kilopixel transition-edge sensor (TES) arrays require new methods to rapidly screen candidate arrays, evaluate array non-idealities in the field, identify outlier devices for removal, and optimize the array performance in the field. We demonstrate robust methods to estimate TES parameters (critical temperatures and thermal conductivity parameters) and their uncertainties using a custom Markov Chain Monte Carlo (MCMC) algorithm. We also constrain systematic effects in estimating the TES parameters from non-isothermal current-voltage curves (IVs) at approximately a ∼3% level. Additionally, for the first time, we have applied Machine Learning (ML) algorithms to tune detector arrays and optimize their performance.

We are developing the frequency division multiplexing (FDM) read-out for the superconducting transition-edge sensors arrays of the X-IFU instrument on board of Athena and of the SAFARI instrument on board of SPICA. An essential component of the FDM is the array of narrow band superconducting resonators, each consisting of lithographically made inductors and capacitors. In the standard FDM configuration, the LC resonators are connected in series with the input coil of a low noise two-stage SQUID amplifier. In this work, we have modified the electrical scheme to weakly couple the SQUID amplifier from the LC filters in order to measure their intrinsic properties. We report on the intrinsic losses and on the noise of high-Q superconducting LC resonators, with resonant frequencies ranging between 1 and 5 MHz, measured at temperatures from 70 to 500 mK. The LC resonators show very low losses with values smaller than $$0.5\,\mathrm {m}\Omega $$ at equilibrium temperatures below 100 mK. We demonstrate that the LC resonators noise is thermal between 500 and 70 mK.

著者人数: 13名, Accepted: 2018-11-23, 資料番号: SA1180407000

We present a superconducting bolometer fabricated by a rolled-up technology that allows one to combine the two-dimensionality (2D) of the superconducting layer with a helical spiral curvature. The bolometer is formed as a free-standing Nb nanohelix acting as an ultrathin transition-edge sensor (TES) and having a negligible thermal contact to the substrate. We demonstrate the functionality of the thin-film TES by examining its microwave-detection performance in comparison with a commercial cryogenic bolometer from QMC Instruments. The nanohelix has been revealed to feature a noise equivalent power (NEP) of about 2 × 10

著者人数: 27名, Accepted: 2018-08-27, 資料番号: SA1180163000

著者人数: 19名, Accepted: 2018-06-19, 資料番号: SA1180159000

The SPICA far-infrared instrument (SAFARI), one of instruments of the space infrared telescope for cosmology and astrophysics, requires a calibration source assembly to calibrate the transition edge sensor readout circuits. A high-performance integrating sphere working at SAFARI wavelength (34–230 µm) is essential. A novel process for preparing terahertz integrating spheres was developed. The aluminum surfaces after sandblasting, wet-etching, and gold plating processes demonstrate rough morphology but high reflectance of 0.91 in 1–10 THz. The spatial distribution of the measured output power excellently agrees with the numerical simulation results based on the assumption of uniform surface radiation at the output port.

The composition of dark matter is one of the puzzling topics in astrophysics. To address this issue, several experiments searching for the existence of axions have been designed, built and realized in the last twenty years. Among all the others, light shining through walls experiments promise to push the exclusion limits to lower energies. For this reason, effort is put for the development of single-photon detectors operating at frequencies $, 15 pages, 7 figures. arXiv admin note: text overlap with arXiv:2011.08745

The authors apply photon number resolving detectors to explore the photon statistics of bimodal microlasers.

We have characterized and mapped the electrical cross talk (ECT) of a frequency division multiplexing (FDM) system with a transition edge sensor (TES) bolometer array, which is intended for space applications. By adding a small modulation at 120 Hz to the AC bias voltage of one bolometer and measuring the cross talk response in the current noise spectra of the others simultaneously, we have for the first time mapped the ECT level of 61 pixels with a nominal frequency spacing of 32 kHz in a 61 × 61 matrix and a carrier frequency ranging from 1 MHz to 4 MHz. We find that about 94% of the pixels show an ECT level of less than 0.4%. Only the adjacent pixels reach this level, and the ECT for the rest of the pixels is less than 0.1%. We also observe higher ECT levels, up to 10%, between some of the pixels, which have bundled long, parallel coplanar wires connecting TES bolometers to inductor-capacitor filters. In this case, the high mutual inductances dominate. To mitigate this source of ECT, the coplanar wires should be replaced by microstrip wires in the array. Our study suggests that an FDM system can have a relatively low ECT level, e.g., around 0.4% if the frequency spacing is 30 kHz. Our results successfully demonstrate a low electrical cross talk for a space FDM technology.

We describe the design and measurement of feedhorn-coupled, transition-edge sensor (TES) polarimeters with two passbands centered at 220 GHz and 280 GHz, intended for observations of the cosmic microwave background. Each pixel couples polarized light in two linear polarizations by use of a planar orthomode transducer and senses power via four TES bolometers, one for each band in each linear polarization. Previous designs of this detector architecture incorporated passbands from 27 GHz to 220 GHz; we now demonstrate this technology at frequencies up to 315 GHz. Observational passbands are defined with an on-chip diplexer, and Fourier-transform-spectrometer measurements are in excellent agreement with simulations. We find coupling from feedhorn to TES bolometer using a cryogenic, temperature-controlled thermal source. We determine the optical efficiency of our device is $\eta$ = 77%$\pm$6% (75%$\pm$5%) for 220 (280) GHz, relative to the designed passband shapes. Lastly, we compare two power-termination schemes commonly used in wide-bandwidth millimeter-wave polarimeters and find equal performance in terms of optical efficiency and passband shape., Comment: Proceedings for the 18th International Workshop on Low Temperature Detectors (LTD18), submitted to the Journal of Low Temperature Physics

Cosmic microwave background (CMB) polarization experiments utilize arrays of low temperature detectors, such as superconducting transition-edge sensor (TES) bolometers. Voltage-biased TES bolometers must be embedded in a readout circuit that allows for stable operation. To ensure stability and to test our physical and electrothermal model of these devices, measurements aimed at characterizing the dynamics of the sensor over the range of detector bias and loading conditions relevant to our application are carried out for multiple bolometer designs. In this work, we present bolometer electrothermal properties derived from current-voltage curves, effective electrothermal time constant measurements, and complex impedance measurements of AlMn TES bolometers intended for the Ali CMB Polarization Telescope (AliCPT). All bolometers consist of 385nm thick 1400 ppma AlMn film with measured superconducting critical temperature Tc = 480 mK. The bolometers are well-described by a simple, one-pole electrothermal model with a natural time constant τ0 that we adjust by varying the leg geometry and the amount of PdAu thermal ballast on the bolometer island. From these measurements, we determine that the volumetric heat capacity of sputtered PdAu (atomic percentages 67.6%/32.4%) at 480mK is 0.22 fJ/(K·μm3). Finally, we present the TES parameters as a function of operational resistance and over a range of loading conditions.

The Origins Space Telescope is one of four flagship missions under study for the 2020 Astrophysics Decadal Survey. With a 5.9 m cold (4.5 K) telescope deployed from space, Origins promises unprecedented sensitivity in the near-, mid-, and far-infrared, from 2.8 - 588 $\mu$m. This mandates the use of ultra-sensitive and stable detectors in all of the Origins instruments. At the present, no known detectors can meet Origins' stability requirements in the near- to mid-infrared, or its sensitivity requirements in the far-infrared. In this work, we discuss the applicability of transition-edge sensors, as both calorimeters and bolometers, to meet these requirements, and lay out a path toward improving the present state-of-the-art., Comment: 43 pages, 8 figures. Accepted for publication by the Journal of Astronomical Telescopes, Instruments, and Systems

Transition Edge Sensors (TESs) are the selected technology for future spaceborne X-ray observatories, such as Athena, Lynx, and HUBS. These missions demand thousands of pixels to be operated simultaneously with high energy-resolving power. To reach these demanding requirements, every aspect of the TES design has to be optimized. Here we present the experimental results of tests on different devices where the coupling between the x-ray absorber and the TES sensor is varied. In particular, we look at the effects of the diameter of the coupling stems and the distance between the stems and the TES bilayer. Based on measurements of the AC complex impedance and noise, we observe a reduction in the excess noise as the spacing between the absorber stem and the bilayer is decreased. We identify the origin of this excess noise to be internal thermal fluctuation noise between the absorber stem and the bilayer. Additionally, we see an impact of the coupling on the superconducting transition in the appearance of kinks. Our observations show that these unwanted structures in the transition shape can be avoided with careful design of the coupling geometry. Also the stem diameter appears to have a significant impact on the smoothness of the TES transition. This observation is still poorly understood, but is of great importance for both AC and DC biased TESs., Comment: 9 pages, 8 figures

We demonstrate multiplexing readout of 60 transition edge sensor (TES) bolometers operating at 90 mK using a frequency division multiplexing readout chain with bias frequencies ranging from 1 to 3.5 MHz and with a typical frequency spacing of 32 kHz. The readout chain starts with a two-stage SQUID amplifier and has a noise level of 9.5 pA/ √{ Hz } . We compare current-voltage curves and noise spectra of TESs measured in a single-pixel mode and in a multiplexing mode. We also map the noise equivalent power (NEP) and the saturation power of the bolometers in both modes, where there are 43 pixels that do not show more than 10% difference in NEP and 5% in saturation power when measured in single pixel and multiplex modes. We have read out a TES with an NEP of 0.45 aW/ √{ Hz } in the multiplexing-mode, which demonstrates the capability of reading out ultra-low noise TES bolometer arrays for space applications.

Large format arrays of transition edge sensor (TES) are crucial for the next generation of X-ray space observatories. Such arrays are required to achieve an energy resolution of $\mathrm{\Delta }E 3 eV full-width-half-maximum (FWHM) in the soft X-ray energy range. We are currently developing X-ray microcalorimeter arrays as a backup option for the X-IFU instrument on board of ATHENA space telescope, led by ESA and foreseen to be launched in 2031. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with (length × width) 140 × 30 $\mu$ m $^2$ TiAu TESs, which have a 2.3 $\mu$ m thick Au absorber for X-ray photons. The pixels have a typical normal resistance $R_{\mathrm{n}}$ = 121 m $\Omega$ and a critical temperature $T_{\mathrm{c}}\sim$ 90 mK. We performed extensive measurements on 60 pixels out of the array in order to show the uniformity of the array. We obtained an energy resolutions between 2.4 and 2.6 eV (FWHM) at 5.9 keV, measured in a single-pixel mode at AC bias frequencies ranging from 1 to 5 MHz, with a frequency domain multiplexing (FDM) readout system, which is developed at SRON/VTT. We also present the detector energy resolution at X-ray with different photon energies generated by a modulated external X-ray source from 1.45 keV up to 8.9 keV. Multiplexing readout across several pixels has also been performed to evaluate the impact of the thermal crosstalk to the instrument's energy resolution budget requirement. This value results in a derived requirement, for the first neighbour, that is less than 1 $\;\times\; 10^{-3}$ when considering the ratio between the amplitude of the crosstalk signal to an X-ray pulse (for example at 5.9 keV).

Precise knowledge of the energy and lifetime of 229mTh isomeric state has notable importance as a basis for a nuclear clock. Such a clock would be capable to extend precision on the oscillator frequency by up to four orders of magnitude compared to the presently best atomic clocks. However, the technique proposed for the clock requires that the isomeric state energy is accessible with existing laser systems. Previous measurement placed this state at ∼8 eV (150 nm), in the Vacuum Ultra Violet (VUV) range of the electromagnetic spectrum. A precise direct measurement of the energy of this state is necessary to determine whether the nuclear clock can be made using existing laser technology. We are developing a cryogenic microcalorimeter to measure the energy and lifetime of the 229mTh isomeric state directly. The experiment will use a 233U source whose alpha-decay will populate the 229mTh isomeric state with 2% probability. The subsequent decay of 229mTh will be measured by a Transition Edge Sensor (TES) with 5 microseconds. The single-photon TES has sufficient resolving power combined with high efficiency in the whole energy band for this experiment. Here we present a prototype of TES based on a 200 nm thick iridium-gold (Ir/Au) film which was tested with a pulsed laser source and demonstrated ∼0.8 eV energy resolution and 5.8 ± 2.1 μs signal recovery time.

The origin and the evolution of the universe are concealed in the evanescent diffuse extragalactic background radiation (DEBRA). To reveal these signals, the development of innovative ultra-sensitive bolometers operating in the gigahertz band is required. Here, we review the design and experimental realization of two bias-current-tunable sensors based on one dimensional fully superconducting Josephson junctions: the nanoscale transition edge sensor (nano-TES) and the Josephson escape sensor (JES). In particular, we cover the theoretical basis of the sensors operation, the device fabrication, their experimental electronic and thermal characterization, and the deduced detection performance. Indeed, the nano-TES promises a state-of-the-art noise equivalent power (NEP) of about $5 \times 10^{-20}$ W$/\sqrt{\text{Hz}}$, while the JES is expected to show an unprecedented NEP of the order of $10^{-25}$ W$/\sqrt{\text{Hz}}$. Therefore, the nano-TES and JES are strong candidates to push radio astronomy to the next level., Comment: 14 pages, 5 figures

The Advanced Atacama Cosmology Telescope Polarimeter (AdvACT) \cite{thornton} is an upgrade for the Atacama Cosmology Telescope using Transition Edge Sensor (TES) detector arrays to measure cosmic microwave background (CMB) temperature and polarization anisotropies in multiple frequencies. The low frequency (LF) array was deployed early 2020. It consists of 292 TES bolometers observing in two bands centered at 27 GHz and 39 GHz. At these frequencies, it is sensitive to synchrotron radiation from our galaxy as well as to the CMB, and complements the AdvACT arrays operating at 90, 150 and 230 GHz. We present the initial LF array on-site characterization, including the time constant, optical efficiency and array sensitivity.

The light in sub-millimeter and far-Infrared (FIR) wavelengths from deep space can travel in an incredibly long distance and contains rich, unique information, which can help astronomers to reveal the history of the universe and answer outstanding questions such as the origin of galaxies, stars, and planets. Sensitive transition edge sensor (TES) bolometers in combination with frequency division multiplexing (FDM) readout system that can read out multiple pixels simultaneously are the candidate detector technology for several space missions operated at sub-millimeter and FIR wavelengths. My thesis reports the study and development of an FDM-readout system for TES bolometers, containing five main scientific sub-projects focusing on building systematically a readout demonstration system. Characterizing the noise of the readout system is essential. Chapter 3 and 4 report studies of the noise from room- and cryogenic-temperature electrical components, respectively. Chapter 5 presents a map of all pixels in the FDM-system, aiming to reduce the unwanted noise between pixels within a TES bolometer array. Chapter 6 demonstrates an FDM-system that can read out 60 low noise TES bolometers simultaneously. The readout noise of the FDM-system is lower than the noise of highly sensitive detectors and that the sensitivities measured when all pixels in operation are the same as what measured when only one pixel is operated. Chapter 7 shows further improved results on electrical-crosstalk performance and stability of the FDM-system compared to Chapter 6. We report a full demonstration of the FDM-system in the lab, opening the door to the readout for space observatories.

The Simons Observatory (SO) is a cosmic microwave background (CMB) survey experiment with three small-aperture telescopes and one large-aperture telescope, which will observe from the Atacama Desert in Chile. In total, SO will field over 60,000 transition edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measure or constrain numerous cosmological quantities, as outlined in The Simons Observatory Collaboration et al. (2019). To verify consistency of fabrication and performance in line with our sensitivity requirements, we will perform in-lab optical tests on isolated SO detectors as well as full detector arrays. The tests include beam measurements, bandpass measurements, and polarization measurements, among others. Here, we will describe the development of a cryogenic testbed that enables optical characterization of SO's detectors. We include the infrared filtering strategy to allow suitable cryogenic performance, design and implementation of the test equipment used in characterization, and the preliminary results from our validation of the testbed's cryo-optical performance.

We are developing ultra-low noise transition edge sensor (TES) bolometer arrays for the long-wavelength grating spectrometer modules of SAFARI, part of the cryogenically-cooled SPICA mission now in phase-A study in Europe. These devices target a per-pixel noise equivalent power (NEP) below 10^-19 WHz^-1/2 with a time-constant faster than 10ms. The SAFARI focal planes will be cooled to 50 mK, and we use a 100 mK thermistor formed from an annealed Titanium-Gold bilayer film. To minimize excess heat capacity, we have developed a new wet-release process which provides high yield in large (~250-pixel) sub-arrays. We will report on the fabrication, testing, and achieved performance of these detectors. We will also present the focal plane assembly designed to support the 5 (spatial) x 180 (spectral) format coupled to spectrometers thru multimodes horns. The focal plane is composed of four monolithic sub-arrays with integrated backshorts, all integrated onto a large silicon substrate.

Large imaging arrays of detectors at millimeter and submillimeter wavelengths have applications that include measurements of the faint polarization signal in the Cosmic Microwave Background (CMB), and submillimeter astrophysics. We are developing planar lenslet arrays for millimeter-wavelength imaging using metamaterials microlithically fabricated using silicon wafers. This metamaterial technology has many potential advantages compared to conventional hemispherical lenslet arrays, including high precision and homogeneity, planar integrated anti-reflection layers, and a coefficient of thermal expansion matched to the silicon detector wafer. Here we describe the design process for a gradient-index (GRIN) metamaterial lenslet using metal-mesh patterned on silicon and a combination of metal-mesh and etched-hole metamaterial anti-reflection layers. We optimize the design using a bulk-material model to rapidly simulate and iterate on the lenslet design. We fabricated prototype GRIN metamaterial lenslet array and mounted it on a Polarbear/Simons Array 90/150~GHz band transition edge sensor (TES) bolometer detector array with sinuous planar antennas. Beam measurements of a prototype lenslet array agree reasonably well with the model simulations. We plan to further optimize the design and combine it with a broadband anti-reflection coating to achieve operation over 70--350~GHz bandwidth., Presented at SPIE Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, December 13-18, 2020

The BICEP3 CMB Polarimeter is a small-aperture refracting telescope located at the South Pole and is specifically designed to search for the possible signature of inflationary gravitational waves in the Cosmic Microwave Background (CMB). The experiment measures polarization on the sky by differencing the signal of co-located, orthogonally polarized antennas coupled to Transition Edge Sensor (TES) detectors. We present precise measurements of the absolute polarization response angles and polarization efficiencies for nearly all of BICEP3s $\sim800$ functioning polarization-sensitive detector pairs from calibration data taken in January 2018. Using a Rotating Polarized Source (RPS), we mapped polarization response for each detector over a full 360 degrees of source rotation and at multiple telescope boresight rotations from which per-pair polarization properties were estimated. In future work, these results will be used to constrain signals predicted by exotic physical models such as Cosmic Birefringence., Comment: Proceedings submitted to SPIE 2020 (AS111). 12 pages, 5 figures, 2 tables

International audience; The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10-16W= p √Hz

Transition Edge Sensor (TES) is a key component for Hot Universe Baryon Survey (HUBS), which is proposed in China to address the so-called “missing baryon problem”. A stable heat sink below 100 mK is needed for the detector’s noise suppression and high resolution. Since HUBS is a satellite based observation mission, a complicated cooling system suitable for space application becomes an important supporting sub-system. A compounded cooling system, including a mechanical cryocooler and an adiabatic magnetization refrigerator (ADR), has been proposed for HUBS. The mechanical cryocooler is used as the pre-cooling 4 K stage, and the ADR is responsible for further reducing the temperature to below 100 mK. High-frequency pulse tube cryocooler (HPTC) and HPTC combined with Joule Thompson cooler (J-T) are two candidates for the mechanical pre-cooling stage, both of which are currently under development. The ADR is being designed and processed. In this paper, we will present the preliminary architecture of the HUBS cooling system, as well as the latest states of HPTC, J-T, and ADR.

Superconducting lithographed resonators have a broad range of current and potential applications in the multiplexed readout of cryogenic detectors. Here, we focus on LC bandpass filters with resonances in the 1-5 MHz range used in the transition edge sensor (TES) bolometer readout of the Simons Array cosmic microwave background (CMB) experiment. In this readout scheme, each detector signal amplitude-modulates a sinusoidal carrier tone at the resonance frequency of the detector's accompanying LC filter. Many modulated signals are transmitted over the same wire pair, and quadrature demodulation recovers the complex detector signal. We observe a noise in the resonant frequencies of the LC filters, which presents primarily as a current-dependent noise in the quadrature component after demodulation. This noise has a rich phenomenology, bearing many similarities to that of two-level system (TLS) noise observed in similar resonators in the GHz regime. These similarities suggest a common physical origin, thereby offering a new regime in which the underlying physics might be probed. We further describe an observed non-orthogonality between this noise and the detector responsivities, and present laboratory measurements that bound the resulting sensitivity penalty expected in the Simons Array. From these results, we do not anticipate this noise to appreciably affect the overall Simons Array sensitivity, nor do we expect it to limit future implementations., 5 pages, 5 figures, accepted to IEEE Transactions on Applied Superconductivity

CMB-S4 is a planned ground-based experiment with scientific impacts reaching from transformative measurements of the cosmic microwave background (CMB) to a deep legacy millimeter-wavelength dataset covering a large fraction of the sky. To meet its ambitious goals, CMB-S4 plans to have small-aperture (0.55-meter) and large-aperture (6-meter) telescopes located both in the Atacama desert (to access a large fraction of are the sky) and at the South Pole (for targeted deep-field observations). A total of over 500,000 superconducting detectors will be distributed across these telescopes, enabling a necessary leap in sensitivity. In this talk, I will give an overview of CMB-S4. I will highlight some of its scientific opportunities as well as presenting the driving technical considerations and the current experimental design.

We are developing an x-ray imaging spectrometer for Super DIOS satellite mission, a future x-ray observatory, planned by JAXA, to be launched in 2030’s. Super DIOS will reveal the nature of the missing baryon in the warm-hot intergalactic medium because of its fine energy and angular resolution, large effective area and large field of view. A main detector on-board Super DIOS consists of a transition-edge sensor (TES) microcalorimeter array of over 30,000 pixels working at a temperature below 100 mK and it poses a considerable technical difficulty to the readout. A microwave superconducting quantum interference device (SQUID) multiplexing is promising technique and expected to achieve a large scale readout of more than 30,000 pixels. We describe our development of a 40-channel microwave SQUID multiplexer with low-noise characteristics∗ and a demonstration of simultaneously reading out 40-pixel TESs. Finally, we discuss a future prospect and a feasibility of reading out an array of more than 30,000 pixels.