Transition Edge Sensor Research Articles

Application of transition-edge sensors for micro-X-ray fluorescence measurements and micro-X-ray absorption near edge structure spectroscopy: a case study of uranium speciation in biotite obtained from a uranium mine.

In this study, we successfully applied a transition-edge sensor (TES) spectrometer as a detector for microbeam X-ray measurements from a synchrotron X-ray light source in the hard X-ray region to determine uranium (U) distribution at the micro-scale and its chemical species in biotite obtained from a U mine. It is difficult to separate the fluorescent X-ray of the U Lα1 line at 13.615 keV from that of the Rb Kα line at 13.395 keV in the X-ray fluorescence spectrum with an energy resolution of approximately 220 eV using a conventional silicon drift detector (SDD). Meanwhile, the fluorescent X-rays of U Lα1 and Rb Kα were fully separated by a TES with 50 eV energy resolution at an energy of around 13 keV. The successful peak separation by the TES led to an accurate mapping analysis of trace U in micro-X-ray fluorescence measurements and a decrease in the signal-to-background ratio in micro-X-ray absorption near edge structure spectroscopy. Thus, it could be a powerful tool for studying the U distribution and speciation in various environmental samples.

Rare event searches with cryogenic detectors

Cryogenic detectors can detect the smallest energy depositions via the scattering of the incoming particle with the detector material. The deposited energy leads to minimal temperature rises of a few μ K , read out via transition edge sensors and SQUIDs. Using scintillating crystals as detector material offers the possibility of discriminating between nuclear recoils from dark matter scattering and electromagnetic background events. The CRESST experiment pioneered this technology and is still among the most sensitive experiments searching for sub-GeV dark matter particles. The technology is now also used by other experiments for dark matter searches (COSINUS) and for measuring coherent elastic neutrino-nucleus scattering (NUCLEUS). We discuss cryogenic detectors’ detection principle and their application. We present the latest dark matter results from CRESST, a new type of background, and the status of the COSINUS and NUCLEUS experiments. This article is part of the theme issue ‘The particle-gravity frontier’.

Nonlinear Kinetic Inductance Sensor

The concept of nonlinear kinetic inductance sensor (NKIS) of electromagnetic radiation is proposed. The idea is based on divergency of kinetic inductanceLk∼dq/dI(ℏqis a momentum of superconducting electrons,Iis a supercurrent) of hybrid superconductor/normal metal (SN) bridge at currentI*Idep(Idepis a depairing current of the hybrid) and temperatureT* much smaller than critical temperatureTc. It makes possible to have large change of phase differenceδϕalong SN bridge in current biased regime atI≃I*even for small electron temperature increase. Appearance ofδϕis accompanied by the change of the current and magnetic flux through the coupled superconducting ring which could be measured with help of superconducting quantum interference device (SQUID). In some respect proposed sensor may be considered as a superconducting counterpart of transition edge sensor (TES) those work is based on large derivativedR/dT(Ris a resistance) nearTc. Because atI≃I*SN bridge is in gapless regime there is no low boundary for frequency of detected electromagnetic radiation. Our calculations show that such a sensor can operate in single photon regime and detect single photons with frequencyν≳10 GHz. We argue that the nontrivial dependenceI(q)of SN bridge could be also used in detectors of continuous electromagnetic radiation, current and magnetic field sensors.

Superconducting transition edge bolometer for high-flux neutron detection

Needs for neutron detection and monitoring in high neutron flux environments are increasing in several different fields. A completely solid-state, current mode bolometric detector is constructed as a solid substrate transition edge sensor based on a high-Tc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_c$$\\end{document} superconducting meander. The detector consists of four individual pixels of which three pixels include 10B4C\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^{10}{\\hbox {B}}_{4}\\hbox {C}}$$\\end{document} neutron absorption layers. The absorbed energy per neutron absorption reaction is modelled and compared to experimental data. The response of the tested detector is directly correlated to a cold neutron beam with a flux of 1.8×108n/cm2/s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1.8\ imes 10^{8}}\\,{\\hbox {n}/{\\hbox {cm}}^2/\\hbox {s}}$$\\end{document} modulated by a slit. The signal is found to be an order of magnitude higher than the thermal background. The dynamics described by the temporal saturation constants is governed by a modulation frequency less than 1Hz\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1}\\hbox { Hz}$$\\end{document}. The thermal response is dynamic and never fully saturates for 50s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${50}\\hbox { s}$$\\end{document} exposures. The efficiency for this proof-of-principle design is 1–2%. Possibilities for optimization are identified, that will increase the efficiency to become comparable to existing solid boron-10 detectors. The existing detectors with event-based read-out have limited functionality in high flux environments. The superconducting bolometer described in this work using current-mode readout will pave the way for high flux applications.

The Cryogenic Anticoincidence Detector for the NewAthena X-IFU Instrument: A Program Overview

Athena (advanced telescope for high-energy astrophysics) is an ESA large-class mission, at present under a re-definition “design-to-cost” phase, planned for a prospective launch at L1 orbit in the second half of the 2030s. It will be an observatory alternatively focusing on two complementary instruments: the X-IFU (X-ray Integral Field Unit), a TES (TransitionEdge Sensor)-based kilo-pixel array which is able to perform simultaneous high-grade energy spectroscopy (~3 eV@7 keV) and imaging over 4′ FoV (field of view), and the WFI (Wide Field Imager), which has good energy spectral resolution (~170 eV@7 keV) and imaging on wide 40′ × 40′ FoV. Athena will be a truly transformational observatory, operating in conjunction with other large observatories across the electromagnetic spectrum available in the 2030s like ALMA, ELT, JWST, SKA, CTA, etc., and in multi-messenger synergies with facilities like LIGO A+, Advanced Virgo+, LISA, IceCube and KM3NeT. The Italian team is involved in both instruments. It has the co-PIship of the cryogenic instrument for which it has to deliver the TES-based Cryogenic AntiCoincidence detector (CryoAC) necessary to guarantee the X-IFU sensitivity, degraded by a primary particle background of both solar and galactic cosmic ray (GCR) origins, and by secondary electrons produced by primaries interacting with the materials surrounding the main detector. The outcome of Geant4 studies shows the necessity for adopting both active and passive techniques to guarantee the residual particle background at 5 × 10−3 cts cm−2 s−1 keV−1 level in 2–10 keV scientific bandwidth. The CryoAC is a four-pixel detector made of Si-suspended absorbers sensed by Ir/Au TESes placed at <1 mm below the main detector. After a brief overview of the Athena mission, we will report on the particle background reduction techniques highlighting the impact of the Geant4 simulation on the X-IFU focal plane assembly design, then hold a broader discussion on the CryoAC program in terms of detection chain system requirements, test, design concept against trade-off studies and programmatic.

Tuning of Critical Temperature and Aging Effect of Ti Films For Superconducting Transition-Edge Sensors

Tuning of Critical Temperature and Aging Effect of Ti Films For Superconducting Transition-Edge Sensors

Magnetic field sensitivity of transition edge sensors

Understanding the magnetic field sensitivity of transition edge sensors (TESs) is vital in optimising the configuration of any magnetic shielding as well as the design of the TESs themselves. An experimental system has been developed to enable the investigation of the applied magnetic field direction on TES behaviour, and the first results from this system are presented. In addition, measurements of the effect of applied magnetic field magnitude on both supercurrent and bias current are presented. The extent to which the current theoretical framework can explain the results is assessed and finally, the impact of this work on the design of TESs and the design of magnetic shielding is discussed.

High kinetic inductance NbTiN films for quantum limited travelling wave parametric amplifiers

A wide-bandwidth and low-noise amplification chain in the microwave regime is crucial for the efficient read-out of quantum systems based on superconducting detectors, such as Microwave Kinetic Inductance Detectors (MKIDs), Transition Edge Sensors (TESs), Magnetic Microcalorimeters (MMCs), and RF cavities, as well as qubits. Kinetic Inductance Travelling Wave Parametric Amplifiers (KI-TWPAs) operated in a three-wave mixing fashion have demonstrated exceptional dynamic range and low-noise performance, approaching the quantum limit. These amplifiers can be fabricated using a single layer of a high kinetic inductance film as weakly dispersive artificial transmission lines, with the ability to control the phase-matched bandwidth through dispersion engineering. In this study, we present the optimisation of the rf sputter-deposition process of NbTiN films using a Nb80%Ti20% target, with the goal of achieving precise control over film characteristics, resulting in high kinetic inductance while maintaining a high transition temperature. The parameter landscape related to the different sputtering conditions, such as pressure, power, and nitrogen flow, has been explored and the film thickness has been used as a fine-tuning parameter to adjust the properties of the final NbTiN films used for the fabrication of KI-TWPAs. As a final result, we have obtained a NbTiN film with a kinetic inductance of 8.5 pH/sq which we have exploited to fabricate KI-TWPA prototype devices, showing promising amplification performance.

Characterization of a hybrid array of single and multi-absorber transition-edge sensor microcalorimeters for the Line Emission Mapper

Characterization of a hybrid array of single and multi-absorber transition-edge sensor microcalorimeters for the Line Emission Mapper

Results from a prototype TES detector for the Ricochet experiment

Coherent elastic neutrino-nucleus scattering (CEνNS) offers valuable sensitivity to physics beyond the Standard Model. The Ricochet experiment will use cryogenic solid-state detectors to perform a precision measurement of the CEνNS spectrum induced by the high neutrino flux from the Institut Laue-Langevin nuclear reactor. The experiment will employ an array of detectors, each with a mass of ∼30 g and a targeted energy threshold of 50 eV. Nine of these detectors (the “Q-Array”) will be based on a novel Transition-Edge Sensor (TES) readout style, in which the TES devices are thermally coupled to the absorber using a gold wire bond. We present initial characterization of a Q-Array-style detector using a 1 gram silicon absorber, obtaining a baseline root-mean-square resolution of less than 40 eV.

A 220 GHz superconducting titanium transition edge sensor array developed for cosmic microwave background experiments

In this paper, we report on the design, fabrication, and characterization of a 220 GHz superconducting transition edge sensor (TES) array developed for ground-based cosmic microwave background (CMB) experiments. Unlike conventional TES arrays adopting thermometers made of bilayer superconducting films, the TES array has thermometers made of simpler single-layer titanium (Ti) film deposited on a suspended silicon nitride (SiN x ) membrane. The thermal weak link is realized by releasing the TES’s thermal island including the Ti thermometer by dry etching with xenon difluoride (XeF2), giving a typical thermal conductance of 25 pW K−1. Its thermal-conductance mechanism is further studied by fitting the measured TES’s complex impedance with a three-block thermal model. The dark and optical noise equivalent power (NEP) of a superconducting TES are both measured. Despite existing lens reflection and dielectric loss in the superconducting microstrip line, its typical optical NEP reaches 100 aW Hz−0.5, which meets the sensitivity requirement for ground-based CMB experiments.

Characterizations of the electrothermal parameters of a transition edge sensor microcalorimeter and its energy resolution

We developed a transition-edge sensor microcalorimeter (μ-calorimeter) using Mo/Au/Au thin films. We report the detector fabrication, the measurements of the electrothermal parameters and the noise characterizations of the transition-edge sensor μ-calorimeters. We estimated the energy resolution of the μ-calorimeter using the measured noise spectrum and the calculated power-to-current responsivity. Using a 55Fe radioactive X-ray source, we characterized the detector responses to incident photons at various working points. The best instrumental energy resolution achieved was 4.13 eV @ 5.9 keV, which agrees qualitatively with the resolution of 4.01 eV estimated from the noise spectrum.

In-Situ Analysis of Chronopotentiometry Data to Predict Electrodeposition Rates

Often in MEMS or NEMS microfabrication R&D, many single layer “test” samples are created prior to committing more complex multiple layer “device” samples which require more time and effort to create. Ideally, much of the R&D can focus on less critical test samples and the experimental results can then be applied to more valuable device wafers. We investigated tin electroforming into patterned polymer molds creating Meissner-Effect Transition-Edge-Sensor (ME-TES) devices1 and found multiple variables changed between the test and device samples making it difficult to target a desired tin metal thickness. These variables were analyzed and distilled down to two: (I) area and (II) the measured voltage at constant current 30 seconds after plating started. In addition to the underlying analysis, a Graphical User Interface (GUI)2 was developed in R to quickly calculate and predict in-situ tin electroplating rates regardless of uncontrolled variables in the sample.ME-TES devices required a final tin plating feature height of 8-12 microns for 50-micron diameter discs coupled with patterned niobium electrical traces3. During chronopotentiometry experiments, two samples were plated for 1 minute and 18 minutes, respectively – both achieving the target height of 10 microns. This extreme variability in rate caused the height to undershoot or overshoot within just a few minutes of plating. Many variables were collected into a database and analyzed including wafer design layout, electrochemical methods, chemistry make-up, electrochemical setup, the use of a reference electrode, current density, voltage, mounting technique, height, device size, and surface roughness across the substrate. The resulting GUI resulted in fewer necessary test samples, reduced processing time, and improved accuracy in plating thickness.(1) Finnegan, P. Packaging & Solid-state Materials and Fabrication Processes. In Packaging & Solid-state Materials and Fabrication Processes, June 2023.(2) St. John, C. “R Shiny User Interface for Electrochemical Development.” In CoDA, Santa Fe NM, March 2023.(3) Arrington, C.L. Optimizing Tin Electroplating for MEMS Meissner-Effect Transition Edge Sensors. In 243rd ECS Meeting with SOFC-XVIII, Boston, MA, 2023.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.SAND2022-10287A

Optimizing Tin Electroplating for MEMS Meissner-Effect Transition-Edge Sensors

Electroforming metal features into patterned polymer molds targeting MEMS microfabrication allows for the enhancement of electrical, mechanical, magnetic, and thermal properties1. Uniform and repeatable electroforming processes are important to achieve the final desired metal geometry to optimize performance. MEMS fabrication processes typically rely on average plating rates based on historical depositions to determine future plating rates and offer the user options to vary electroplating time, among other options, to meet the desired device height(s). Process repeatability is often difficult to achieve in these scenarios and can be challenging in R&D applications with limited throughput. Inherent changes from one sample to the next can occur in many forms including a change in active area of lithographically patterned photoresist molds, resistance of substrates/seed layers below electroplated layers, geometry of the layout, chemistry make-up, electroplating setup, and fast deposition rates can all affect plating rates from sample to sample. Some changes can be controlled through careful inspection and tracking, then accounted for. However, some changes cannot be observed, and deposition rates can change from sample to sample leading to ever-changing plating rates.These challenges were encountered during electroplating of tin disks coupled with planar superconducting coils of niobium targeting the microfabrication of Meissner-Effect Transition-Edge Sensor devices (ME-TES)2. We investigated two and three electrode setups using a modified Dow Chemical Solderon make-up chemistry targeting pure tin depositions as opposed to tin and silver alloy depositions. Those changes were coupled with chronopotentiometry, chronoamperometry, and pulse plating experiments to optimize tin electrodeposition. Once found, the optimum tin deposition process was built into a graphical user interface (GUI)3 that predicts electroplating rates and was then successfully applied to microfabricate ME-TES’s. This process methodology could benefit other metal MEMS-based electrodeposition processes such as nickel, copper, gold, magnetic alloys, etc. to optimize electroplating.(1) Buchheit, T. E.; Christenson, T. R.; Schmale, D. T.; Lavan, D. A. Understanding and tailoring the mechanical properties of LIGA fabricated materials. Materials Science of Microelectromechanical Systems (Mems) Devices 1999, 546, 121-126. DOI: Doi 10.1557/Proc-546-121.(2) Finnegan, P. Packaging & Solid-state Materials and Fabrication Processes. In Packaging & Solid-state Materials and Fabrication Processes, June 2023.(3) St. John, C. In-Situ Analysis of Chronopotentiometry Data to Predict Electrodeposition Rates. In 243rd ECS Meeting with SOFC-XVIII, Boston, MA, 2023.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525 SAND2022-10288A

Advances in superconductor quantum and thermal detectors for analytical instruments

Analytical instruments or scientific instruments are indispensable for scientific research and industry. The analytical instruments require a detector that converts physical quantities to be measured (measurands) to electric signals. This Tutorial describes the basics of quantum and thermal detectors, the operation principles of superconductor detectors, and the ultimate performance of state-of-art analytical instruments with superconductivity. We still face fundamental issues, such as the classical Fano factor, the relation between energy gap and mean carrier creation energy, quasiparticle dynamics, and the intermediate state in the middle of superconducting transition; and engineering issues, such as the small sensitive area and the spatially nonuniform response. Nevertheless, enormous efforts have matured superconductor detectors, which enables us to solve the inherent problems of conventional analytical instruments. As an example of the analytical results, we describe x-ray spectroscopy and mass spectrometry at our institute by using three detector types: superconductor tunnel junction, transition edge sensor, and superconductor strip. Microwave kinetic inductance and metallic magnetic calorimetric types are also described. The analytical results may contribute to a wide range of fields, such as dentistry, molecular biology, energy-saving society, planetary science, and prebiotic organic molecules in space.

Progress Toward Transition Edge Sensor Arrays With On-Chip Thermal Stabilization

Electrothermal feedback in a transition edge sensor (TES) suppresses thermal fluctuations in the TES and well-thermally coupled regions in proximity. We have designed a heavily metallized, leg-isolated membrane with a TES which serves as a thermal isolation stage that can be lithographically integrated with other devices, for example, a suitably designed TES detector. Through modeling, fabrication, and test of prototype devices, we plan to examine the utility of stabilizing this guard stage to limit low frequency variability in the sensor response. In one implementation, a leg-isolated TES bolometer of higher superconducting transition temperature ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i> ) is encircled by a second membrane region which is metallized and thermally stabilized by a second, lower- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i> TES. We present fabrication results on the dual- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_c</i> device and explore varied heat capacity of the thermal stability stage in the single-pixel design. We then evaluate the use of this stage for multiple pixel arrangements and investigate the criteria for stabilizing such a device.

A Tabletop X-Ray Tomography Instrument for Nanometer-Scale Imaging: Demonstration of the 1,000-Element Transition-Edge Sensor Subarray

We report on the 1,000-element transition-edge sensor (TES) x-ray spectrometer implementation of the TOMographic Circuit Analysis Tool (TOMCAT). TOMCAT combines a high spatial resolution scanning electron microscope (SEM) with a highly efficient and pixelated TES spectrometer to reconstruct three-dimensional maps of nanoscale integrated circuits (ICs). A 240-pixel prototype spectrometer was recently used to reconstruct ICs at the 130 nm technology node, but to increase imaging speed to more practical levels, the detector efficiency needs to be improved. For this reason, we are building a spectrometer that will eventually contain 3,000 TES microcalorimeters read out with microwave superconducting quantum interference device (SQUID) multiplexing, and we currently have commissioned a 1,000 TES subarray. This still represents a significant improvement from the 240-pixel system and allows us to begin characterizing the full spectrometer performance. Of the 992 maximimum available readout channels, we have yielded 818 devices, representing the largest number of TES x-ray microcalorimeters simultaneously read out to date. These microcalorimeters have been optimized for pulse speed rather than purely energy resolution, and we measure a FWHM energy resolution of 14 eV at the 8.0 keV Cu K$\alpha$ line.

Fabrication of a 64-Pixel TES Microcalorimeter Array With Iron Absorbers Uniquely Designed for 14.4-keV Solar Axion Search

If a hypothetical elementary particle called an axion exists, to solve the strong CP problem, a 57Fe nucleus in the solar core could emit a 14.4-keV monochromatic axion through the M1 transition. If such axions are once more transformed into photons by a 57Fe absorber, a transition edge sensor (TES) X-ray microcalorimeter should be able to detect them efficiently. We have designed and fabricated a dedicated 64-pixel TES array with iron absorbers for the solar axion search. In order to decrease the effect of iron magnetization on spectroscopic performance, the iron absorber is placed next to the TES while maintaining a certain distance. A gold thermal transfer strap connects them. We have accomplished the electroplating of gold straps with high thermal conductivity. The residual resistivity ratio (RRR) was over 23, more than eight times higher than a previous evaporated strap. In addition, we successfully electroplated pure-iron films of more than a few micrometers in thickness for absorbers and a fabricated 64-pixel TES calorimeter structure.

Demonstration of a Full-Scale Brassboard TES Microcalorimeter Array for the Athena X-IFU

We have characterized a full-scale transition-edge sensor (TES) microcalorimeter array as a milestone towards the demonstration of technology readiness level (TRL) 5 for the detector array for the X-ray Integral Field Unit (X-IFU) instrument on ESA's future flagship X-Ray Observatory called Athena. We fabricated a 90 mm full-scale prototype TES array and measured the properties and the performance in a newly developed platform in which up to 960 out of ∼3,200 pixels can be read out. In this paper, we report on measurements of the uniformity of the transition temperature and shape, the uniformity of the spectral energy resolutions at 7 keV and 10 keV, the thermal crosstalk for the first, the diagonal, and the second nearest neighbors, and the energy sensitivities to environment perturbations for the magnetic field, the TES bias voltage, and the heat bath temperature.

Correcting Gain Drift in TES Detectors for Future X-Ray Satellite Missions

Changes in the operating environment of transition-edge sensor (TES) microcalorimeters can cause variations in the detector gain function over time. If not corrected, this can degrade the spectral resolution, and cause systematic errors in the knowledge of the absolute energy. The non-linear nature of the TES energy scale function and the potential for multiple, simultaneous sources of drift can make effective corrections extremely challenging. Satellite instruments typically employ an on-board calibration source to provide known reference X-ray lines. This allows real-time monitoring of the detector gain stability and provides information that can be used to correct for drifts. Here we discuss progress towards demonstrating that the energy scale requirements can be met for future instruments such as Athena X-IFU. We present measurements (from ∼ 1-12 keV) on ∼ 200 pixels in a prototype X-IFU array. We use a non-linear drift correction algorithm that uses two fiducial calibration lines (5.4 keV and 8.0 keV) to track gain and interpolate a new, corrected gain between a set of three pre-calibrated gain functions that span the anticipated range of induced drifts. We demonstrate this algorithm is effective at correcting the full gain scale in the presence of multiple sources of environmental drift.