Transition Edge Sensor Devices Research Articles

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.

Characterization of Transition Edge Sensors for the Simons Observatory

The Simons Observatory is building both large (6 m) and small (0.5 m) aperture telescopes in the Atacama desert in Chile to observe the cosmic microwave background (CMB) radiation with unprecedented sensitivity. Simons Observatory telescopes in total will use over 60,000 transition edge sensor (TES) detectors spanning center frequencies between 27 and 285 GHz and operating near 100 mK. TES devices have been fabricated for the Simons Observatory by NIST, Berkeley, and HYPRES/SeeQC corporation. Iterations of these devices have been tested cryogenically in order to inform the fabrication of further devices, which will culminate in the final TES designs to be deployed in the field. The detailed design specifications have been independently iterated at each fabrication facility for particular detector frequencies. We present test results for prototype devices, with emphasis on NIST high frequency detectors. A dilution refrigerator was used to achieve the required temperatures. Measurements were made both with 4-lead resistance measurements and with a time domain Superconducting Quantum Interference Device (SQUID) multiplexer system. The SQUID readout measurements include analysis of current vs voltage (IV) curves at various temperatures, square wave bias step measurements, and detector noise measurements. Normal resistance, superconducting critical temperature, saturation power, thermal and natural time constants, and thermal properties of the devices are extracted from these measurements.

A two-dimensional resistor network model for transition-edge sensors with normal metal features

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 (2D) normal metal features on the TES transition shape. In this work, we approach this problem by treating the TES as a 2D 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 2D geometric features. Our 2D 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.

Stable temperature regulation for TES testing below 200mK employing improved Cohen-Coon method

Transition Edge Sensor (TES) is a promising low-temperature detector technology for high-resolution X-ray spectroscopy. Hot Universe Baryon Surveyor (HUBS) is a satellite concept proposed in China to address so-called “missing baryon problem”, which has serious implications on the formation and evolution of galaxies. At the heart of HUBS is a soft X Ray spectrometer based on TES operating below 100 mK. In the developing phase, the characterization of TES requires high accuracy and stable temperature regulation. Typically, 10 μK temperature fluctuation would be needed over the temperature range of 50 mK to 200 mK. To achieve this accuracy, we designed and built a cold plate in a dilution refrigerator, which regulates temperature on the cold plate with a PID controller. To improve the stability of temperature regulation, Cohen-Coon method is employed and optimized experimentally. Over the desired temperature range, the temperature of the cold plate can be regulated stably and accurately. At typical transition temperatures of our TES devices, temperature fluctuation is well controlled, e.g., within 8 μK (rms) fluctuation at 100 and 200 mK.

Modelling of Freestanding Membrane-Supported Superconducting Al/Ti Bilayer Transition Edge Sensor Bolometer

The aim of this research work was to model the behaviour of a transition edge sensor (TES) bolometer by applying curve fitting methodology on empirical data. Data obtained from the experiments were used to plot characteristic curves to find resistance–temperature (R–T) and current–voltage (I–V) relations. The measurements were taken by using a cryogenic-free 3He refrigerator with a least temperature of 320 mK. Least-squares curve fitting technique was used to devise the equations of the experimentally obtained data. Similarly, the empirical data and estimated curves were validated using the parameters of R-squared, sum of squares due to error (SSE), adjusted R-squared, and root-mean-squared error (RMSE). By comparing the plot of the empirical data and estimated behaviour curves showed high degree of similarity, and hence it was established that these equations could be used to estimate the bolometer’s operating behaviour for different ambient conditions with minimal percentage error. We also studied etched (TES device suspended on SiN) and non-etched (Si substrate based device) samples of bolometers. It was concluded that bolometers made up of etched sample of TES are appropriate for use in millimetre and submillimeter waves, especially for cosmic microwave background polarization detection.

Analysis and Simulation of AC-Biased TES Circuits

We systematically study the analysis and simulation of ac-biased superconductor transition-edge sensor (TES) circuits. In these ac-biased circuits, the current and voltage of the TES experience large swings in both directions, and small-signal analysis around a dc steady state does not apply. To understand their electrical and thermal behavior, we rely on concepts and techniques from radio-frequency circuit simulation and introduce the periodic steady state and perform periodic ac analysis. We also construct TES device models based on a comprehensive two-fluid physical model and investigate the behavior of ac-biased TES circuits using advanced circuit simulators. By relating our findings to results for the analysis of dc-biased TES circuits, we give appropriate definitions for the current and temperature sensitivity of the TES in ac-biased circuits. Our work not only builds a rigorous foundation for theoretical analysis of ac-biased TES circuits but also introduces powerful simulation techniques valuable for their design and research.

Transition Edge Sensor (TES) X-Ray Detecting System with Sensitivity Correction to Stabilize the Spectrum Peak Center

Transition Edge Sensor (TES) is an energy dispersive X-ray detecting system with high energy resolution. The energy resolution of this system depends on the steepness of superconducting transition curve from normal to superconducting state, heat capacitance and the operating temperature. The TES is based on the dilution refrigerator cooled by about 100 mK. The energy resolution is calculated about 1-2 eV for the detector with maximum detecting energy as 10 eV. The energy resolution also depends on the superconducting current flowing through the TES device because the superconducting current is affected by the temperature stability of the refrigerator. The fluctuation of the superconducting current means the fluctuation of the X-ray spectrum peak center. We have developed the sensitivity correction system to stabilize the peak center of the X-ray spectrum. The peak center of X-ray spectrum correlates with heater power to keep the base temperature of TES device at a constant temperature. The peak center of X-ray spectrum is calibrated by monitoring the heater power at constant time interval using the correlation curve between the peak center of X-ray spectrum and heater power.

Optical Efficiency and R(T,I) Measurements of ACTPol TESes Using Time Domain Multiplexing Electronics

We present new data on feedhorn-coupled transition-edge sensor devices fabricated for the second-generation receiver (ACTPol) for the Atacama cosmology telescope (ACT). First, we describe optical efficiency measurements of the latest ACTPol detector wafer, which has a $$86\,\pm 15\,\%$$ average optical efficiency. Next, we discuss measurements of the TES resistance as a function of temperature and bias current ( $$R(T,I)$$ ) using the ACTPol time-domain multiplexing electronics. Qualitative agreement between $$R(T,I)$$ data at low bias current and the two-fluid model prediction is shown. Using the two-fluid model and low bias current $$R(T,I)$$ data, $$\alpha $$ and $$\beta $$ at our operating bias current are calculated.

TES Development for a Frequency Selective Bolometer Camera

We discuss the development, at Argonne National Laboratory (ANL), of a four-pixel camera with four spectral channels centered at 150, 220, 270, and 360 GHz. The scientific motivation involves photometry of distant dusty galaxies located by Spitzer and SCUBA, as well as the study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich effect in clusters, and galactic dust. The camera incorporates Frequency Selective Bolometer (FSB) and superconducting Transition-Edge Sensor (TES) technology. The current generation of TES devices we examine utilizes proximity effect superconducting bilayers of Mo/Au, Ti, or Ti/Au as TESs, located along with frequency selective absorbing structures on silicon nitride membranes. The detector incorporates lithographically patterned structures designed to address both TES device stability and detector thermal transport concerns. The membrane is not perforated, resulting in a detector which is comparatively robust mechanically. In this paper, we report on the development of the superconducting bilayer TES technology, the design and testing of the detector thermal transport and device stability control structures, optical and thermal test results, and the use of new materials.

Toward ultimate performance limits of thermoelectric (QVD) detectors

‘QVD’ detectors are based on thermoelectric heat-to-voltage (Q→V) conversion and digital (V→D) readout. In theory, they are competitive with superconducting tunnel junction detectors and transition edge sensor devices. We analyze the performance of the QVD detectors with different design architectures. It is concluded that the detectors with lanthanum–cerium hexaboride sensors can be very fast: up to 100MHz counting rates for UV photons. In addition to traditional astrophysical applications, these detectors can be applied to the tasks of quantum computing and communication.