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The implementation of utilizing superconducting quantum interference device (SQUID) readout for constant voltage biased transition edge sensors (TES) has enabled the detection of the infinitesimal fluctuation in cosmic microwave background (CMB). The properties of the fluctuations will provide us the information of the universe at the time that this light was first emitted. In short, by measuring the CMB today, we learn about the distant, ancient universe—how the universe began, what it is made of, and how it evolved to its current state. Over the past 20 years, we have achieved many successful CMB measurements with Josephson junctions. Brian, I offer my congratulations on your eight decades of life—Happy 80th birthday!

One way of making a transition-edge sensor (TES) is by utilizing the proximity effect, in which the $$T_{C}$$ of a superconducting film is reduced with a normal metal film in metallic contact. The $$T_{C}$$ of a bilayer TES can be estimated by solving the Usadel equations with given boundary conditions. The classical boundary conditions of a bilayer include a specific interface resistance being temperature-independent. In this paper, we will introduce a temperature-dependent specific interface resistance. By fitting the measured $$T_{C}$$ data of Ir/Au bilayers from the literature to a $$T_{C}$$ calculation model, we will compare the fit parameters and fit errors with the temperature-dependent specific interface resistance described in this work and with the classical temperature-independent specific interface resistance.

Transition-edge sensors (TESs) are capable of highly accurate single particle energy measurement. TESs have been used for a wide range of photon detection applications, particularly in astronomy, but very little consideration has been given to their capabilities as electron calorimeters. Existing electron spectrometers require electron filtering optics to achieve energy discrimination, but this step discards the vast majority of electrons entering the instrument. TESs require no such energy filtering, meaning they could provide orders of magnitude improvement in measurement rate. To investigate the capabilities of TESs in electron spectroscopy, a simulation pipeline has been devised. The pipeline allows the results of a simulated experiment to be compared with the actual spectrum of the incident beam, thereby allowing measurement accuracy and efficiency to be studied. Using Fisher information, the energy resolution of the simulated detectors was also calculated, allowing the intrinsic limitations of the detector to be separated from the specific data analysis method used. The simulation platform has been used to compare the performance of TESs with existing X-ray photoelectron spectroscopy (XPS) analysers. TESs cannot match the energy resolution of XPS analysers for high-precision measurements but have comparable or better resolutions for high count rate applications. The measurement rate of a typical XPS analyser can be matched by an array of 10 TESs with 120 microsecond response times and there is significant scope for improvement, without compromising energy resolution, by increasing array size., Comment: 9 pages, 3 figures

The state-of-the-art technology of X-ray microcalorimeters based on superconducting transition edge sensors (TESs), for applications in astrophysics and particle physics, is reviewed. We will show the advance in understanding the detector physics and describe the recent breakthroughs in the TES design that are opening the way towards the fabrication and the read-out of very large arrays of pixels with unprecedented energy resolution. The most challenging low temperature instruments for space- and ground-base experiments will be described., 48 pages, 14 figures, published in Appl. Sci. 2021, 11, 3793

In the framework of the ESA X-ray mission ATHENA, scheduled for launch in 2030, an ESA Core Technology Program (CTP) was started in 2016 to build a flight like cryostat demonstrator in parallel with the phase A studies of the ATHENA/X-IFU instrument. As part of this CTP, called the Detector Cooling System (DCS), design, manufacturing and test of a cryostat including existing space coolers will be done. In addition to the validation of thermal performance, a Focal Plan Assembly (FPA) demonstrator using Transition Edge Sensors (TES) detector technology will be also integrated and its performance characterized versus the environment provided by the cryostat. This is a unique opportunity to validate many crucial issues of the cryogenic part of such a sensitive instrument. A dedicated activity within this CTP-DCS is the demonstration of the 300 K–50 mK cooling chain in a Ground System Equipment (GSE) cryostat. The studies are focused on the operation of the space coolers, which is made possible by the use of a ground cooler for cooling cryogenic shields and mechanical supports. This test program is also the opportunity to validate the operation of the cryochain with respect to various requirements, such as time constant and temperature stabilities. This would bring us valuable inputs to integrate the cryochain in DCS cryostat, X-IFU studies, SPICA and LiteBIRD missions. This paper is focused on the operation of the full 300 K–50 mK cryochain. In particular, the recycling options of the sub Kelvin cooler (sorption cooler + an ADR) versus the capability of 4 K and 2 K JT coolers are described. Results on the JT parameters validation campaign are summarized and eventually the results of the coupled test with sub Kelvin cooler will be presented and discussed.

We are developing Frequency Domain Multiplexing (FDM) read-out of Transition-Edge Sensors (TESs) for the X-ray Integral Field Unit (X-IFU) on board of the future European X-Ray observatory Athena. The X-IFU Focal-Plane Assembly consists of a $sim$ 3000-pixel array, read out by SQUID-based FDM. The multiplexing readout scheme is a critical technology for the X-IFU instrument because of the cooling and electronic power limits for the satellite. In this contribution, we report on the development of FDM readout technology and on the performance of TESs array under an AC bias at MHz frequencies.

HOLMES is an experiment aiming at performing a direct measurement of the neutrino mass from the electron capture (EC) spectrum of $$^{163}\hbox {Ho}$$. In order to reach a sensitivity of the order of $$\sim $$1 eV/c$$^2$$ on the neutrino mass, it is necessary to gather as many as $$10^{13}$$ events in the 3-year projected live time of HOLMES, keeping the pileup fraction as low as $$10^{-4}$$. This is not a trivial matter when it comes to low- temperature calorimeters, which usually have a rather slow time response. At the same time, a large number of detectors need to be operated simultaneously, and hence, in order to avoid an extremely large cryogenic facility, multiplexing is required. In this contribution, I will outline the current status and perspective of HOLMES, with special care devoted to the detectors and readout system, which have currently reached their target performance.

To cope with the foreseen demand for tungsten-based TESs in the current and future phases of the CRESST experiment, we investigated the possibility to implement a reliable, simple and reproducible fabrication method using sputtering. In this contribution, we present the method under development for tungsten deposition using conventional magnetron sputtering with xenon as sputtering gas. TESs with transition temperatures ($$T_c$$Tc) down to 15 mK have been obtained with transition widths smaller than 1 mK. We also give a first assessment on the reproducibility of the process and present the potential for tuning of the $$T_c$$Tc.

We present critical temperature measurements of titanium thin films annealed in an argon atmosphere at various temperatures. We are able to depress the $${T}_{\text {C}}$$ by up to 200 mK from an initial $${T}_{\text {C}}$$ of 540 mK by increasing the temperature at which the films are post-annealed from 80 to 275 $$^{\circ }$$ C. We find an anti-correlation trend between the annealing temperature and the measured $${T}_{\text {C}}$$ . We also briefly discuss how we plan to use these films to produce TES detectors to be used in the LSPE/SWIPE balloon-borne cosmic microwave background polarimeter, which is slated to launch in December 2019.

This paper proposes and studies the concept of admissible edge-dependent average dwell time (AED-ADT) which characterizes a kind of new switching signals for switched systems. The switching behavior of the proposed switching signal is denoted by a directed graph, where each admissible transition edge (ATE) signifies a switching from one subsystem to another. New stability criteria for switched systems with AED-ADT switching are then derived. The choices of transition weights of ATEs make the proposed AED-ADT switching more general than mode-dependent average dwell time (MDADT) switching. Stabilization conditions for switched linear systems are also established by designing state-feedback switching controller whose gain matrices can be obtained by solving linear matrix inequalities. The effectiveness of the proposed approaches is demonstrated by a numerical example.

The R(T, I) shape of the superconducting transition in transition edge sensors (TESs) is of crucial importance to determine their ultimate performance. This paper reports a study of the temperature and current dependences of the transition of Mo/Au TESs, focused on the low resistance region, where these devices preferentially operate. A large broadening of the transition is observed when increasing the applied current. An empirical analytic expression for R(T, I) is found, which describes the transition of devices with different critical temperatures, from R = 0 up to at least 30% Rn (in some cases nearly 80% Rn). Several mechanisms for this behaviour are considered; results show that a current assisted vortex pair unbinding mechanism (Berezinskii–Kosterlitz– Thouless transition) could be the possible origin for this behaviour. Finally, the consequences of the current-induced transition broadening for TES properties and operation are outlined., Work funded by the Spanish Ministerio de Economía y Competitividad (MINECO, project ESP2016-76683-C3-2-R) and the European Commission (H2020 project AHEAD: Integrated Activities for the high energy astrophysics domain’). Personnel from ICMAB acknowledge financial support from MINECO, through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-04969). We kindly thank Professor R Navarro for a critical reading of the manuscript.

A refined selected-codes based test method for pipelined ADC is presented. By selecting a set of specific codes and a self-correction mechanism implementation, the proposed method leverages the redundancy characteristic of the Pipelined ADC to reduce the number of output codes in linearity test after a comprehensive consideration of the comparator offset, capacitance mismatch, gain error, and input noise. Experimental evaluation on a 10-bit 1.5-bit/stage Pipelined ADC as test model has proved that the test data has decreased to 7% compared to the traditional method while maintaining a level of accuracy by minimizing the error of mapping between the comparator and the transition edge. The proposed method efficiently decrease the test cost and heightening the test accuracy.

Transition-edge sensors (TESs) can be used in high-resolution photon detection, exploiting the steep slope of the resistance in the superconducting-to-normal transition edge. Normal metal bars on the TES film are commonly used to engineer its transition shape, namely the dependence of resistance on temperature and current. This problem has been studied in one dimension, however until now, there have been no predictive models of the influence of two-dimensional (2-D) normal metal features on the TES transition shape. In this work, we approach this problem by treating the TES as a 2-D network of resistors, the values of which are based on the two-fluid model. We present a study of the behavior of devices with different 2-D geometric features. Our 2-D network model is capable of predicting how typical TES geometry parameters, such as number of bars, bar spacing, and overall dimensions, influence device behavior and thus is a powerful tool to guide the engineering of new TES devices.

Transition edge sensors (TES) have recently been developed at CERN as second sound detectors for quench localisation on superconducting radio frequency (SRF) cavities. After validation of the concept of heat source localisation by TES in the laboratory, TES have been implemented as a diagnostic tool in SRF vertical testing cryostats at CERN SM18 facility. Two cavities were forced to quench by applying sufficiently high values of RF power. Simultaneously, RF and TES second sound signals were recorded. In this paper we present the particularities of each of the relevant tests, the nature of the read signals, as well as the analysis performed on them to locate the origin of the quenching spot.

The detection of second sound in He-II can be exploited during superconducting cavity testing to locate the germ of a quench. The sudden appearance of a hotspot generates this wave in the helium II bath, which is routinely detected by Oscillating Superleak Transducers (OST) reacting to the first arrived inter-component velocity front. Recently, we have developed Transition Edge Sensors (TES) that are able to detect second sound by measuring directly the temperature fluctuation of second sound (below milli-Kelvin, in sub-millisecond time scale) with a good native signal-to-noise ratio. We present the current state of development of second sound detectors based on TES, experiments aiming to characterize more thoroughly their behaviour as second sound detectors by thermometry, and the capabilities they provide in terms of localisation of the heat source in the case of direct sight.

The concept of a superconducting transition-edge bolometer with rf readout, which was proposed in a number of earlier publications, is analyzed. It is shown that such a device cannot in fact operate at the edge of the superconducting transition, and nonequilibrium effects in the superconductor play the major role in its response to the electromagnetic action. A mathematical model is developed, which explains qualitatively the experimental results reported earlier and indicating an unstable response to the action of a readout (pump) signal. The possibility of obtaining a stable response with an optimal choice of parameters of the device is also demonstrated.

Sensor geometry can be used to tune the properties of AC-biased high resistance transition edge sensors.

The transition-edge sensor (TES) technology is widely applied to X-ray spectroscopy or imaging applications at wavelengths ranging from infrared to sub-mm, with the aim of potentially achieving unprecedented spectral resolution and detection sensitivity. As a critical component of the X-ray microcalorimeter, the TES affects the energy resolution via two main parameters: temperature sensitivity and current sensitivity. Tremendous efforts have been made to fabricate TESs with high temperature sensitivity and low current sensitivity, in order to enhance the energy resolution of the microcalorimeters. However, since the resistance of TESs is a complex function of temperature, current, and magnetic field, it is difficult to optimize the operational point of the detector from the first principle. We conducted an experiment to map the parameter space of a sample of MoAu TESs in the transition phase. The results show that the current sensitivity depends only on the resistance of the TESs, which is in line with the two-fluid model. The figure of merit of energy resolution dependence on the quasiparticle diffusion length has been compared with the prediction of the two-fluid model, which indicates that the time-averaging critical current of phase-slip centers is not a constant throughout the superconducting transition. The magnetic field could potentially enhance the energy resolution by reducing the charge imbalance relaxation time.

Transition Edge Sensors are ultra-sensitive superconducting detectors with applications in many areas of research, including astrophysics. The device consists of a superconducting thin film, often with additional normal metal features, held close to its transition temperature and connected to two superconducting leads of a higher transition temperature. There is currently no way to reliably assess the performance of a particular device geometry or material composition without making and testing the device. We have developed a proximity effect model based on the Usadel equations to predict the effects of device geometry and material composition on sensor performance. The model is successful in reproducing I −V curves for two devices currently under study. We use the model to suggest the optimal size and geometry for TESs, considering how small the devices can be made before their performance is compromised. In the future, device modelling prior to manufacture will reduce the need for time-consuming and expensive testing.

For the last few decades, micro-channel plates (MCPs), charged coupled devices (CCDs), and hybrid complementary metal-oxide-semiconductor (CMOS) detectors have been the workhorses for collecting photons. More recently, the development of superconducting detectors such as the superconducting tunnel junctions (STJs) and transition edge sensors (TESs) has generated excitement in the imaging community. These detectors provide for simultaneous timing and spectral information as well as relatively good spectral energy resolution. However, STJs and TESs suffer from the major challenge of constructing large format arrays which are required for most imaging applications. Kinetic Inductance Detectors (KIDs) are a relatively new alternative superconducting technology that has many of the same desirable characteristics of STJs and TESs, and offer great promise for creating large-scale formats like current CCDs and CMOS detectors. The current approach for photon detection with KIDs uses a multiple frequency component activation signal. While this method has been proven to enable detection of photons, it has three key drawbacks that limit its utility in remote, size and power constrained applications. The first drawback is that each element of a KID array must be individually characterized under precisely controlled conditions. A second, even greater challenge is that the response of each KID element changes with temperature, necessitating in-system recalibration. Finally, current KIDs require 4-stage cryo-coolers in order to operate at mK temperatures, which are more challenging for space applications. New stimulation and detection approaches for arrays of high-temperature (∼4K) KID sensors are being investigated to simplify the electronics required for the source signal and reduce the impact of even small changes in temperature. Simplification of sensor electronics will enable large and robust arrays of high-temperature KID sensors, opening new photon sensing opportunities in size, mass, and power-constrained applications. This paper describes the current state of SwRI's Internal Research and Development effort to develop a KID detector and associated support hardware.

Accepted: 2015-11-30, 資料番号: SA1160043000

The bilayers of Transition Edge Sensors (TESs) are often modified with additional normal-metal features such as bars or dots. Previous device measurements suggest that these features improve performance, reducing electrical noise and altering response times. However, there is currently no numerical model to predict and quantify these effects. Here we extend existing techniques based on Usadel's equations to describe TESs with normal-metal features. We show their influence on the principal TES characteristics, such as the small-signal electrothermal parameters $\alpha$ and $\beta$ and the superconducting transition temperature $T_{c}$. Additionally, we examine the effects of an applied magnetic field on the device performance. Our model predicts a decrease in $T_{c}$, $\alpha$ and $\beta$ as the number of lateral metal structures is increased. We also obtain a relationship between the length $L$ of a TES and its critical temperature, $T_{c} \propto L^{-0.7}$ for a bilayer with normal-metal bars. We predict a periodic magnetic flux dependence of $\alpha, \beta$ and $I_{c}$. Our results demonstrate good agreement with published experimental data, which also show the reduction of $\alpha$, $\beta$ and $T_{c}$ with increasing number of bars. The observed Fraunhofer dependence of critical current on magnetic flux is also anticipated by our model. The success of this model in predicting the effects of additional structures suggests that in the future numerical methods can be used to better inform the design of TESs, prior to device processing.

We have fabricated multilayer readout wiring Transition Edge Sensors (TES), which enable us to realize both large effective area and high-energy resolution for future X-ray astrophysical missions, such as DIOS. By sandwiching a SiO2 insulation layer between Al superconducting signal and return lines, self/mutual inductances and self fielding of bias leads are expected to be reduced. We fabricated 4x4 and 20x20 TES array on the multilayer wiring and tested their performance. Under the low temperature condition, several pixels in the TES array showed sharp superconducting transitions at around ~300 mK. We also succeeded in detecting X-ray signals from the 4x4 TES, contrary to the previous results of 20x20 TES. We further investigated the reasons for the differences between the 4x4 TES and the 20x20 TES, and present future plans for improving the multilayer TES array fabrication., Comment: 6 pagas, 4 figures, LTD15

We propose a simplified current–voltage (IV) relation for the analysis and simulation of superconductor transition-edge sensor (TES) circuits. Compared to the conventional approach based on the effective TES resistance, our expression describes the device behavior more thoroughly covering the superconducting, transitional, and normal-state for TES currents in both directions. We show how to use our IV relation to perform small-signal analysis and derive the device's temperature and current sensitivities based on its physical parameters. We further demonstrate that we can use our IV relation to greatly simplify TES device modeling and make SPICE simulation of TES circuits easily accessible. We present some interesting results as examples of valuable simulations enabled by our IV relation.

BICEP3 is a 520 mm aperture, compact two-lens refractor designed to observe the polarization of the cosmic microwave background (CMB) at 95 GHz. Its focal plane consists of modularized tiles of antenna-coupled transition edge sensors (TESs), similar to those used in BICEP2 and the Keck Array. The increased per-receiver optical throughput compared to BICEP2/Keck Array, due to both its faster f/1.7 optics and the larger aperture, more than doubles the combined mapping speed of the BICEP/Keck program. The BICEP3 receiver was recently upgraded to a full complement of 20 tiles of detectors (2560 TESs) and is now beginning its second year of observation (and first science season) at the South Pole. We report on its current performance and observing plans. Given its high per-receiver throughput while maintaining the advantages of a compact design, BICEP3-class receivers are ideally suited as building blocks for a 3rd-generation CMB experiment, consisting of multiple receivers spanning 35 GHz to 270 GHz with total detector count in the tens of thousands. We present plans for such an array, the new "BICEP Array" that will replace the Keck Array at the South Pole, including design optimization, frequency coverage, and deployment/observing strategies., 17 pages, 6 figures. To be published in Proc. SPIE. Presented at SPIE Astronomical Telescopes and Instrumentation Conference 9914: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, June 2016

Spider, the Keck Array, and BICEP2 are projects to study the polarization of the cosmic microwave background (CMB). All three use large format arrays of antenna-coupled, membrane-isolated, transition edge sensors (TES’s). Although similar, each project requires its own set of device parameters, such as thermal conductance, time constants, and normal state resistances. We have perfected a fabrication process that achieves two primary objectives: (1) high device yields of 95% or greater, and (2) very low spreads in devices parameters. Currently our arrays are taking science data at the South Pole in both the BICEP2 and Keck array telescopes. The focal planes for Spider, a high altitude balloon mission, are on schedule for a 2012 deployment. An overview of fabrication and development is given as well as a snapshot of scientific data.

SRON is developing an electronic read-out system for an array of transition edge sensors (TES), which combines the techniques of frequency domain multiplexing (FDM) with base-band feedback (BBFB). An important part of this technique is implemented in digital electronics. This paper describes how a significant reduction of the power consumption of the digital electronics is realized by down-sampling to much lower frequencies using channelization and a poly-phase filter design adapted to BBFB.

Single photon detectors are fundamental devices in several scientific fields, like in optical science and technology. We introduce the state of the art of Transition Edge Sensors, developed and characterized at INRIM, to detect photons from optical to near-infrared wavelength range (406–1570 nm). Both the capability to resolve up to 29 incident photons in a single pulse and to discriminate up to 2 photons with an energy resolution of 0.18 eV have been reached.

We present an update on the performance of our 2 mm bolometer camera GISMO (the Goddard IRAM 2 Millimeter Observer), which is used for astronomical observations at the IRAM 30 m Telescope. The camera is optimized to efficiently observe dusty high-redshift galaxies. GISMO uses a monolithic 8 by 16 Backshort Under Grid (BUG) array with superconducting Transition Edge Sensors (TES). It serves as a testbed for our close-packed superconducting bolometer technologies and guides us in optimizing the design of future fast, low background bolometer cameras. Illustrated by astronomical observations we obtained recently, we demonstrate the scientific potential of the camera, highlighted by the detection of two high redshift galaxies.

Photon-number discriminating detectors are fundamental to new quantum photon-based standards. We report results on superconducting transition-edge sensors based on Ti/Au and Ti/Pd bilayers allowing pulses containing up to five photons to be discriminated.

In this paper, the underlying principles of superconductivity for the typical microwave engineer was presented and the superconducting properties that can be exploited in microwave and millimeter-wave technologies was described to yield components into appreciable performance enhanced over conventional systems. Some of these microwave technologies in superconductor discussed were; microwave superconductivity, superconductor microwave device technology, superconducting communications filters, microwave superconductivity for high-energy physics applications, superconducting transition edge bolometers, superconducting digital microwave technology, and refrigeration.

We report on the performance of the digital baseband feedback circuit developed to readout and process signals from arrays of transition edge sensors for SPICA-SAFARI in frequency domain multiplexing (FDM). The standard procedure to readout the SQUID current amplifiers is to use a feedback loop (flux-locked loop: FLL). However the achievable FFL bandwidth is limited by the cable transport delay t d , which makes standard feedback inconvenient. A much better approach is to use baseband feedback. We have developed a model of the electronic readout chain for SPICA-SAFARI instrument by using an Anlog-digital co-simulation based on Simulink-System Generator environment.

We report on the development of transition edge sensors for x-ray detection. The sensor technology was based on the fabrication of a superconducting film on a thin membrane. A bilayer of a superconductor, Ti, and a noble metal, Au, was e-beam evaporated on a micromachined SiNx. Another Au layer was evaporated on the two side edges of the bilayer in order not to be affected by structural imperfections at the boundaries. With the method described in the present report, the superconducting transition temperature of the device was consistently achieved to near 80 mK with a sharp transition. The energy spectrum ueasured with the device provided 37 eV FWHM for 5.9 x-rays. We also discuss the design and fabrication considerations as well as the performance of the device in detail.

We investigated the possibility of using transformers to replace SQUIDs for the readout of microcalorimeters. This simple scheme has been used in the past for bolometers, however it was discarded for the use with TES microcalorimeters because of the inadequate performance. Our work shows that, with a few simple changes, the performance of transformers as current transducers, while still not comparable to that of SQUIDs, is sufficient to read out the signal from TES microcalorimeters without any degradation in speed or energy resolution. In contrast to SQUIDs, transformers do not dissipate any power and their working principle makes them natural candidates for frequency multiplexing. Their extension to several channels is therefore straightforward.

We have studied the noise spectra of Au/Ti bilayer transition-edge sensors with transition temperatures around ∼100 mK. The sensors did not include an absorber element, and were patterned into either a circular Corbino geometry, or a Corbino disk divided into four parallel sections. Both sensor types contained noise in excess of the thermodynamic phonon noise and the equilibrium Johnson noise of the sensor. However, the divided Corbino detector had a significantly lower noise level than the undivided Corbino disk, especially at bias points below the mid-point of the transition.

We present results from an experiment to develop bilayer metallic films of Al and Au as superconducting transition edge thermometers for the detection of third sound waves in thin superfluid 4He films. We compare transition edge data for such an Al/Au thermometer to that for a pure Zn thermometer and document its utility for third sound detection.

An extended treatment of microcalorimeters functioning including large signal analysis reveals some important aspects that have never been described before. Outside the small signal approximation, transition edge sensors have a non linear response which needs to be studied and understood. This is accomplished in this paper. Furthermore, the electrothermal feedback shortens the recovery time which cannot be anymore described by a unique decay time, since during the restoring process it changes considerably with the temperature inside the sensor transition.

In recent years microcalorimeters and bolometers have achieved impressive performance in terms of energy resolution or Noise Equivalent Power (NEP). However their performance is still significantly worse than predicted by ideal models. The difference is due primarily to non‐ideal effects that have to be taken into account and to additional noise of unknown origin. The most significant non‐ideal effects have been quantified and include hot‐electron and absorber decoupling and the related extra noise sources, and non‐ohmic behavior of the thermometer. Excess noise of unknown origin is particularly significant when Transition Edge Sensors (TES) detectors are used as thermometers and is currently under experimental and theoretical investigation. This paper reviews the origin of non‐ideal effects in microcalorimeters and bolometers and their effect on energy resolution and NEP. It also reviews the status of theoretical and experimental results on the characterization of the excess noise in TES, and in particul...

Computer simulations of the operation of high- T c superconducting bolometers in the constant voltage and constant current biasing modes were carried out. Thermophysical parameters of practically employed membrane bolometers and microbolometers were used for the calculations.

Measuring the neutrino mass is one the most compelling issue in particle physics. HOLMES is an experiment funded by the European Research Council for a direct measurement of neutrino mass. HOLMES will perform a precise measurement of the end point of the Electron Capture decay spectrum of 163Ho in order to extract information on neutrino mass with a sensitivity as low as 1 eV. HOLMES, in its final configuration will deploy a 1000 pixel array of low temperature microcalorimeters: each calorimeter consists of an absorber, where the Ho atoms will be implanted, coupled to a Transition Edge Sensor thermometer. The detectors will be kept at the working temperature of ∼70 mK using a dilution refrigerator. In order to gather the required 3 × 1013 events in a three year long data taking with a pile up fraction as low as 10-4, detectors must fulfill rather high speed and resolution requirements, i.e. 10 μs rise time and 4 eV resolution. To ensure such performances with an efficient read out technique for very large detectors array kept at low temperature inside a cryostat is no trivial matter: at the moment, the most appealing read out technique applicable to large arrays of Transition Edge Sensors is rf-SQUID multiplexing. It is based on the use of rf-SQUIDs as input devices with flux ramp modulation for linearisation purposes; the rf-SQUID is then coupled to a super-conductive λ/4-wave resonator in the GHz range, and the modulated signal is finally read out using the homodyne technique.

SAFARI is an infrared instrument developed by a European based consortium to be flown in SPICA, a Japanese led mission. The SAFARI detectors are transition edge sensors (TES) and require temperatures down to 50 mK for their operation. For that purpose we have developed a hybrid architecture based on the combination of a 300 mK sorption stage and a small adiabatic demagnetization stage. An engineering model has been designed to provide net heat lifts of 0.4 and 14 μW respectively at 50 and 300 mK, with an overall cycle duration of 48 h and a duty cycle objective of over 75%. The cooler is self-contained, fits in a volume of 156 × 312 × 182 mm and is expected to weigh 5.1 kg. It has been designed to withstand static loads of 120 g and a random vibration level of 21 g RMS.

instrument’s twin focal planes, each with over 5000 superconducting Transition Edge Sensors (TES) that work simultaneously at 450 and 850 microns are producing excellent science results and in particular a unique series of JCMT legacy surveys. In this paper we give an update on the performance of the instrument over the past 2 years of science operations and present the results of a study into the noise properties of the TES arrays. We highlight changes that have been implemented to increase the efficiency and performance of SCUBA-2 and discus the potential for future enhancements.