Transition Edge Sensor Research Articles

Sensitivity Modeling for LiteBIRD

LiteBIRD is a future satellite mission designed to observe the polarization of the cosmic microwave background radiation in order to probe the inflationary universe. LiteBIRD is set to observe the sky using three telescopes with transition-edge sensor bolometers. In this work we estimated the LiteBIRD instrumental sensitivity using its current design. We estimated the detector noise due to the optical loadings using physical optics and ray-tracing simulations. The noise terms associated with thermal carrier and readout noise were modeled in the detector noise calculation. We calculated the observational sensitivities over fifteen bands designed for the LiteBIRD telescopes using assumed observation time efficiency.

Frequency division multiplexing readout of a transition edge sensor bolometer array with microstrip-type electrical bias lines.

We demonstrate multiplexed readout of 43 transition edge sensor (TES) bolometers operating at 90 mK using a frequency division multiplexing (FDM) readout chain with bias frequencies ranging from 1 to 3.5MHz and a typical frequency spacing of 32kHz. We improve the previously reported performance of our FDM system by two important steps. First, we replace the coplanar wires with microstrip wires, which minimize the cross talk from mutual inductance. From the measured electrical cross talk (ECT) map, the ECT of all pixels is carrier leakage dominated. Only five pixels show an ECT level higher than 1%. Second, we reduce the thermal response speed of the TES detectors by a factor of 20 by increasing the heat capacity of the TES, which allows us to bias all TES detectors below 50% in transition without oscillations. We compare the current-voltage curves and noise spectra of the TESs measured in single-pixel mode and multiplexing mode. We also compare the noise equivalent power (NEP) and the saturation power of the bolometers in both modes, where 38 pixels show less than 10% difference in NEP and 5% difference in saturation power when measured in the two different modes. The measured noise spectrum is in good agreement with the simulated noise based on measured parameters from an impedance measurement, confirming that our TES is dominated by phonon noise.

Development of Superconducting Single-Photon and Photon-Number Resolving Detectors for Quantum Applications

Single-photon detectors based on superconducting thin films have become a viable class of technologies for widespread usage in quantum optics. In this tutorial paper we introduce the key performance metrics required of them for quantum information processing and related fields. We review the latest records achieved by such devices, study technical details regarding recent improvements in superconducting nanowire detectors and transition-edge sensors, and present representative applications in cutting-edge research areas that benefit from these advances.

A SQUID controller unit for space-based TES sensor readout

We have developed a Superconducting Quantum Interference Device (SQUID) controller unit for Transition Edge Sensors (TES) readout, designed to be used in a space mission. The unit is made of 8 boards and each board can condition four SQUID array amplifiers. The board design is inspired by a similar one developed for ground based experiments, but specific changes have been made to adopt Components Off The Shelf (COTS) with space grade equivalents, to implement redundancy and cross-strapping capabilities. The design also includes the thermal path to lift the heat off the boards towards an in-house designed monolithic aluminum rack.

Frequency domain multiplexing readout for large arrays of transition-edge sensors

We report our most recent progress and demonstration of a frequency domain multiplexing (FDM) readout technology for transition-edge sensor (TES) arrays, both of which we have been developing in the framework of the X-IFU instrument on board the future Athena X-ray telescope. Using Ti/Au TES micro-calorimeters, high-Q LC filters and analog/digital electronics developed at SRON and low-noise two-stage SQUID amplifiers from VTT Finland, we demonstrated the feasibility of our FDM readout technology, with the simultaneous readout of 37 pixels with an energy resolution of 2.23 eV at an energy of 6 keV. We finally outline our plans for further scaling up and improving our technology in the future.

An Examination of Thermal Coupling of an Ir/Au TES for TORIO-229 Experiment

The TORIO-229 experiment aims for a direct model-independent determination of the transition energy of ^mathrm {229m}Th produced in ^mathrm {233}U alpha decay. This knowledge will be of interest for the development of a scientific clock exploiting the thorium isomeric state, which would be able to significantly surpass the precision of the presently best clocks. As a detector for the isomeric transition, it is planned to use an array of fast transition-edge sensors (TESs) which demonstrated to be feasible in our previous work where the Ir/Au TES prototype demonstrated 4.6pm 1.7 µs rise time, 5.8pm 2.1 µs fall time and 0.789pm 0.023 eV energy resolution and signal-to-noise ratio of sim10 with one-photon (2.824 eV) signal, satisfying the experimental requirements. Such a microcalorimeter will allow to register the transition in every possible channel in the energy range from 3 to 50 eV and with a lifetime of > 5 µs. To have a full characterization of a single TES for the final detector array design, its thermal conductance has to be measured. In this contribution, we report on a test measurement of thermal coupling of a TORIO-229 prototype-like iridium-gold TES.

High-resolution Compton spectroscopy using x-ray microcalorimeters.

X-ray Compton spectroscopy is one of the few direct probes of the electron momentum distribution of bulk materials in ambient and operando environments. We report high-resolution inelastic x-ray scattering experiments with high momentum and energy transfer performed at a storage-ring-based high-energy x-ray light source facility using an x-ray transition-edge sensor (TES) microcalorimeter detector. The performance was compared with a silicon drift detector (SDD), an energy-resolving semiconductor detector, and Compton profiles were measured for lithium and cobalt oxide powders relevant to lithium-ion battery research. Spectroscopic analysis of the measured Compton profiles demonstrates the high-sensitivity to the low-Z elements and oxidation states. The line shape analysis of the measured Compton profiles in comparison with computed Hartree-Fock profiles is usually limited by the resolution of the semiconductor detector. We have characterized an x-ray TES microcalorimeter detector for high-resolution Compton scattering experiments using a bending magnet source at the Advanced Photon Source with a double crystal monochromator, providing monochromatic photon energies near 27.5keV. The momentum resolution below 0.16 atomic units (a.u.) was measured, yielding an improvement of more than a factor of 7 over a state-of-the-art SDD for the same scattering geometry. Furthermore, the lineshapes of narrow valence and broad core electron profiles of sealed lithium metal were clearly resolved using an x-ray TES compared to smeared and broadened lineshapes observed when using the SDD. High-resolution Compton scattering using the energy-resolving area detector shown here presents new opportunities for spatial imaging of electron momentum distributions for a wide class of materials with applications ranging from electrochemistry to condensed matter physics.

Optimized Detector Design of Transition-Edge Sensors for the Calorimetry of Carbon Ion Beams

Optimized Detector Design of Transition-Edge Sensors for the Calorimetry of Carbon Ion Beams

Low-threshold sapphire detector for rare event searches

Low mass nuclear recoil dark matter and coherent-elastic-neutrino-nucleus-scattering (CEνNS) searches confront similar challenges in choosing ultra-low threshold and large-mass detectors. We report experimental results from a 100 g single-crystal sapphire detector design with a diameter of 76 mm and thickness of 4 mm instrumented with transition edge sensors (TES). Sapphire is a crystal of aluminum oxide (Al2O3) and has been found to be a good candidate for light mass dark matter search experiments due to its lower atomic mass compared to other detector materials such as germanium and silicon. This new phonon-assisted sapphire detector was characterized to yield a baseline recoil energy resolution of 28.4 ± 0.4 eV. The detector is designed to be sensitive to low-energy rare interactions with an intention to investigate the low-mass region of dark matter phase-space and search for CEνNS at the reactor site.

The TES detector of the ALPS II experiment

The Any Light Particle Search II (ALPS II) experiment is a Light-Shining-through-a-Wall experiment under construction at DESY, Hamburg. Its goal is to probe the existence of Axion Like Particles (ALPs), a possible candidate for dark matter. The expected small rate of reconverted photons requires a sensor capable of measuring low-energetic photons (1.165 eV) with high efficiency and a low dark count rate. A first science run in 2022 will be based on a heterodyne detection scheme. For a second run, a Transition Edge Sensor (TES) system is envisioned as a photon-counting detector. The TES reacts to the change in temperature produced by the absorption of a single photon by operating in the transition between the superconducting and normal conducting phases. Due to its high sensitivity, the TES is susceptible to the influence of electronic noise and background events. In this work, we perform analyses in time and frequency domain and compare these results with simulations to understand the detector’s energy resolution. The setup of the TES is presented, along with the proposed design to measure its efficiency and linearity.

Development of Self-aligned Ti Optical Transition-Edge Sensors at 1550 nm

Development of Self-aligned Ti Optical Transition-Edge Sensors at 1550 nm

Devices for Thermal Conductivity Measurements of Electroplated Bi for X-ray TES Absorbers

Electroplated bismuth (Bi) is commonly used in transition-edge sensors (TESs) for X-rays because of its high stopping power and low heat capacity (Collan in Phys Rev B 1:2888, 1970, Yan in Appl Phys Lett 111:192602, 2017). Electroplated Bi is usually grown on top of another metal that acts as seed layer, typically gold (Au), making it challenging to extrapolate its thermoelectric properties. In this work, we present four-wire resistance measurement structures that allow us to measure resistance as a function of temperature of electroplated Bi independently of Au. The results show that the thermal conductivity of the Bi at 3 K is high enough to ensure the correct thermalization of X-ray photons when used as an absorber for TESs.

Simons Observatory Focal-Plane Module: In-lab Testing and Characterization Program

The Simons Observatory is a ground-based cosmic microwave background instrument to be sited in the Atacama Desert in Chile. SO will deploy 60,000 transition-edge sensors (TES) bolometers in 49 separate focal-plane modules across a suite of four telescopes covering three dichroic bands termed low frequency (LF), mid-frequency and ultra-high frequency. Each MF and UHF focal-plane module packages 1720 feedhorn-coupled detectors with cryogenic components for highly multiplexed readout using microwave SQUID multiplexing. In this paper, we describe the testing program we have developed for high-throughput validation of modules after they are assembled. The validation requires measurements of the yield, saturation powers, time constants, noise properties and optical efficiencies. Additional measurements will be performed for further characterization as needed. We describe the methods developed and demonstrate preliminary results from the initial testing of a prototype module.

Low Noise Frequency-Domain Multiplexing of TES Bolometers Using SQUIDs at Sub-Kelvin Temperature

Digital Frequency-Domain Multiplexing (DfMux) is a technique that uses MHz superconducting resonators and Superconducting Quantum Interference Device (SQUID) arrays to read out sets of transition edge sensors. DfMux has been used by several Cosmic Microwave Background experiments, including most recently POLARBEAR-2 and SPT-3 G with multiplexing factors as high as 68, and is the baseline readout technology for the planned satellite mission LiteBIRD. Here, we present recent work focused on improving DfMux readout noise, reducing parasitic impedance, and improving sensor operation. We have achieved a substantial reduction in stray impedance by integrating the sensors, resonators, and SQUID array onto a single-carrier board operated at 250 mK. This also drastically simplifies the packaging of the cryogenic components and leads to better-controlled crosstalk. We demonstrate a low readout noise level of 8.6 mathrm{pA/Hz}1^{1/2}, which was made possible by operating the SQUID array at a reduced temperature and with a low dynamic impedance. This is a factor of two improvement compared to the achieved readout noise level in currently operating Cosmic Microwave Background experiments using DfMux and represents a critical step toward maturation of the technology for the next generation of instruments.

First measurements of remoTES cryogenic calorimeters: Easy-to-fabricate particle detectors for a wide choice of target materials

Low-temperature calorimeters based on a readout via Transition Edge Sensors (TESs) and operated below 100mK are well suited for rare event searches with outstanding resolution and low thresholds. We present first experimental results from two detector prototypes using a novel design of the thermometer coupling denoted remoTES, which further extends the applicability of the TES technology by including a wider class of potential absorber materials. In particular, this design facilitates the use of materials whose physical and chemical properties, as e.g. hygroscopicity, low hardness and low melting point, prevent the direct fabrication of the TES onto their surface. This is especially relevant in the context of the COSINUS experiment (Cryogenic Observatory for SIgnals seen in Next-Generation Underground Searches), where sodium iodide (NaI) is used as absorber material.With two remoTES detector prototypes operated in an above-ground R&D facility, we achieve baseline energy resolutions of σ=87.8eV for a 2.33g silicon absorber and σ=193.5eV for a 2.27g α-TeO2 absorber, respectively. RemoTES calorimeters offer – besides the wider choice of absorber materials – a simpler production process combined with a higher reproducibility for large detector arrays.

Calibration of Transition-edge Sensor (TES) Bolometer Arrays with Application to CLASS

The current and future cosmic microwave background (CMB) experiments fielding kilopixel arrays of transition-edge sensor (TES) bolometers require accurate and robust gain calibration methods. We simplify and refactor the standard TES model to directly relate the detector responsivity calibration and optical time constant to the measured TES current I and the applied bias current I b. The calibration method developed for the Cosmology Large Angular Scale Surveyor (CLASS) TES bolometer arrays relies on current versus voltage (I–V) measurements acquired daily prior to CMB observations. By binning Q-band (40 GHz) I–V measurements by optical loading, we find that the gain calibration median standard error within a bin is 0.3%. We test the accuracy of this I–V bin detector calibration method by using the Moon as a photometric standard. The ratio of measured Moon amplitudes between the detector pairs sharing the same feedhorn indicates a TES calibration error of 0.5%. We also find that, for the CLASS Q-band TES array, calibrating the response of individual detectors based solely on the applied TES bias current accurately corrects TES gain variations across time but introduces a bias in the TES calibration from data counts to power units. Since the TES current bias value is set and recorded before every observation, this calibration method can always be applied to the raw TES data and is not subject to I–V data quality or processing errors.

Search for sub-GeV dark matter via the Migdal effect with an EDELWEISS germanium detector with NbSi transition-edge sensors

The EDELWEISS collaboration reports on the search for Dark Matter (DM) particle interactions via Migdal effect with masses between $32$ MeV$\cdot$c$^{-2}$ to $2$ GeV$\cdot$c$^{-2}$ using a $200$ g cryogenic Ge detector sensitive to simultaneously heat and ionization signals and operated underground at the Laboratoire Souterrain de Modane in France. The phonon signal was read out using a Transition Edge Sensor made of a NbSi thin film. The detector was biased at $66$ V in order to benefit from the Neganov-Trofimov-Luke amplification and resulting in a resolution on the energy of electron recoils of $4.46$ eV$_{ee}$ (RMS) and an analysis threshold of $30$ eV$_{ee}$. The sensitivity is limited by a dominant background not associated to charge creation in the detector. The search constrains a new region of parameter space for cross-sections down to $10^{-29}$ cm$^2$ and masses between $32$ and $100$ MeV$\cdot$c$^{-2}$. The achieved low threshold with the NbSi sensor shows the relevance of its use for athermal-phonon sensitive devices for low-mass DM searches.

Modeling a Three-Stage SQUID System in Space with the First Micro-X Sounding Rocket Flight

The Micro-X sounding rocket is a NASA funded X-ray telescope payload that completed its first flight on July 22, 2018. This event marked the first operation of Transition Edge Sensors (TESs) and their SQUID-based multiplexing readout system in space. Unfortunately, due to an ACS pointing failure, the rocket was spinning during its five minute observation period and no scientific data was collected. However, data collected from the internal calibration source marked a partial success for the payload and offers a unique opportunity to study the response of TESs and SQUIDs in space. Of particular interest is the magnetic field response of the NIST MUX06a SQUID readout system to tumbling through Earth's magnetic field. We present a model to explain the baseline response of the SQUIDs, which lead to a subset of pixels failing to "lock" for the full observational period. Future flights of the Micro-X rocket will include the NIST MUX18b SQUID system with dramatically reduced magnetic susceptibility.

Absolute Energy Measurements with Superconducting Transition-Edge Sensors for Muonic X-ray Spectroscopy at 44 keV

Superconducting transition-edge sensor (TES) microcalorimeters have great utility in x-ray applications owing to their high energy resolution, good collecting efficiency and the feasibility of being multiplexed into large arrays. In this work, we develop hard x-ray TESs to measure the absolute energies of muonic-argon ($\mu$-Ar) transition lines around 44 keV and 20 keV. TESs with sidecar absorbers of different heat capacities were fabricated and characterized for their energy resolution and calibration uncertainty. We achieved ~ 1 eV absolute energy measurement accuracy at 44 keV, and < 12 eV energy resolution at 17.5 keV.

Development of the Characterization Methods Without Electrothermal Feedback for TES Bolometers for CMB Measurements

Superconducting Transition-Edge Sensor (TES) bolometers are used for cosmic microwave background (CMB) observations. We used a testbed to evaluate the thermal performance of TES bolometers in regard to the saturation power Psat and intrinsic thermal time constant tau0. We developed an evaluation method that is complementary to methods with electrothermal feedback. In our method, the antenna termination resistor of the bolometer is directly biased with DC or AC electric power to simulate optical power, and the TES is biased with small power, which allows Psat and tau0 to be determined without contribution from the negative electrothermal feedback. We describe the method and results of the measurement using it. We evaluated Psat of five samples by applying DC power and confirmed the overall trend between Psat and the inverse leg length. We evaluated tau0 of the samples by applying DC plus AC power, and the measured value was reasonable in consideration of the expected values of other TES parameters. This evaluation method enables us to verify whether a TES has been fabricated with the designed values and to provide feedback for fabrication for future CMB observations.