Browsing by Author "Chervenak, J. A."
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Item Characterizing Thermal Background Events for Athena X-IFU(IEEE, 2023-03-14) Hull, S. V.; Adams, J. S.; Bandler, S. R.; Beaumont, Sophie; Chervenak, J. A.; Cumbee, R.; Finkbeiner, F. M.; Ha, J. Y.; Kelley, R. L.; Kilbourne, C. A.; Porter, F. S.; Sakai, Kazuhiro; Smith, S. J.; Wakeham, Nicholas; Wassell, E. J.; Yoon, S. H.The X-ray Integral Field Unit on Athena will be subject to a cosmic-ray induced thermal background on orbit, with energy depositions into the detector wafer leading to thermal bath fluctuations. Such fluctuations have the potential to degrade energy resolution performance of the transition-edge sensor based microcalorimeter. This problem was previously studied in simulations that modeled thermal bath fluctuations induced by cosmic-ray events and evaluated the resulting energy resolution degradation due to a simulated timeline of such events. Now taking an experimental approach, we present results using a collimated Am-241 alpha particle source to deposit a known energy to specific locations on the detector wafer. Thermal pulses induced by the alpha particle energy depositions are measured at various detector pixels for several different experimental configurations, including for energy deposited into the inter-pixel structure of the wafer, as well as the frame area outside the pixel array. Further, we also test both with and without a thick backside heatsinking metallization layer that is baselined for the instrument. In each case results are compared to expectations based on the thermal model developed for the previous study.Item Correcting Energy Estimation Errors Due to Finite Sampling of Transition‑Edge Sensor Data(Springer, 2022-03-30) Witthoeft, M. C.; Adams, J. S.; Bandler, S. R.; Beaumont, S.; Chervenak, J. A.; Eckart, M. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, Antoine; Porter, F. S.; Sakai, K.; Smith, S. J.; Wakeham, Nicholas; Wassell, E. J.We are developing transition-edge sensor microcalorimeters for the X-ray integral field unit (X-IFU) on-board ESA’s Athena space telescope. These detectors will be read out using time-domain multiplexing. Due to the limitations on bandwidth and dynamic range of the readout, the optimally filtered pulse heights of the measured X-ray signals suffer from a nonlinear variation with the exact photon arrival time relative to the sampling points. The shape and magnitude of this variation depend on the photon energy. We describe a method to characterize this energy-dependent variation with few parameters, which can then be interpolated to correct event energies across the whole spectrum. We implement our method on measurements from 200 pixels in a prototype X-IFU kilo-pixel array readout using 8-column × 32-row TDM. We show that the interpolation errors between calibration points, over the energy range 4–12 keV, can be made sufficiently small that they do not adversely impact the measured energy resolution across the full spectral range.Item Demonstration of Fine-Pitch High-Resolution X-ray Transition-Edge Sensor Microcalorimeters Optimized for Energies below 1 keV(Springer Nature Switzerland AG., 2020-03-07) Sakai, K.; Adams, J. S.; Bandler, S. R.; Beaumont, S.; Chervenak, J. A.; Datesman, A. M.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, A. R.; Porter, F. S.; Sadleir, J. E.; Smith, S. J.; Wakeham, N. A.; Wassell, E. J.; Jaeckel, F. T.; McCammon, D.; Eckart, M. E.; Ryu, K.In this paper, we report on X-ray transition-edge sensor (TES) microcalorimeters optimized to have the best possible energy resolution for a limited energy range for the incoming X-rays, such as an energy resolution of 0.3 eV full width half maximum (FWHM) for energies up to ≈0.8keV as is desirable for one of the Lynx X-ray Microcalorimeter subarrays. The test array we have fabricated has 60×60 sensors on a pitch of 50μm, and has 46×46μm² absorbers that are one micrometer thick. We have measured a spectral energy resolution of the same device using 3 eV photons delivered through an optical fiber. For the one-photon 3 eV line, we have obtained an energy resolution of 0.25 eV FWHM, which is consistent with the estimated performance based on the signal size and noise. Further measurements will determine how the energy resolution degrades with energy. Based upon measurements of the TES transition characteristics, it appears that this level of energy resolution should be achievable up to 0.5 keV, and the performance will then gradually degrade to the measured energy resolution of around 2.3 eV at 1.5 keV. In this paper, we describe the full design and characterization of this detector, and discuss the performance limits of pixels designs like this.Item Developments of Laboratory-Based Transition-Edge Sensor Readout Electronics Using Commercial-Off-The-Shelf Modules(Springer, 2022-08-16) Sakai, Kazuhiro; Adams, J. S.; Bandler, S. R.; Beaumont, S.; Chervenak, J. A.; Doriese, W. B.; Durkin, M.; Finkbeiner, F. M.; Hull, S. V.; Kelley, R. L.; Kilbourne, C. A.; Muramatsu, H.; Porter, F. S.; Reintsema, C. D.; Smith, S. J.; Wakeham, Nicholas; Wassel, E. J.We are developing lab-based readout electronics for Transition-edge sensors (TES) using commercial-of-the-shelf (COTS) modules. These COTS modules are advantageous since they increase development speed and keep the cost low. We have developed these electronics to support both non-multiplexed and time-division multiplexing (TDM) readout systems. The system utilizes remote control via Ethernet, and the interface allows many types of measurements to be automated. With the TDM readout system, we have achieved 2.05 eV at 6 keV, 2.1 eV at 7 keV, 2.3 eV at 8 keV, and 2.8 eV at 12 keV with 2-column×32-row multiplexing. We will be using this system in the characterization of detectors for the X-Ray Integral Field Unit (X-IFU) instrument on Athena. In this paper, we present an overview of the design and their performance.Item Effects of Normal Metal Features on Superconducting Transition-Edge Sensors(Springer, 2018-04-02) Wakeham, Nicholas; Adams, J. S.; Bandler, S. R.; Chervenak, J. A.; Datesman, A. M.; Eckart, M. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, Antoine; Porter, F. S.; Sadleir, J. E.; Sakai, Kazuhiro; Smith, Stephen J.; Wassell, E. J.; Yoon, W.In transition-edge sensors (TESs), the addition of normal metal stripes on top of the superconducting bilayer, perpendicular to the current direction, is known to globally alter the sensitivity of the resistance R to changes in temperature T and current I. Here, we describe measurements of the dependence of the TES current on magnetic field B, bath temperature and voltage bias in devices with various numbers of stripes. We show that the normal metal features have a profound effect on the appearance of localized regions of very large (T/R) dR/dT . We associate this with changes in the current distribution and corresponding changes in the oscillatory pattern of I(B). 140 µm TESs with no stripes are found to have a relatively smooth resistive transition and sufficiently low noise that the measured energy resolution is 1.6 eV for X-rays of 1.5 keV. The predicted energy resolution at 6 keV is better than 2 eV, once the heat capacity is optimized for these higher energies.Item High-Frequency Noise Peaks in Mo/Au Superconducting Transition-Edge Sensor Microcalorimeters(Springer, 2020-01-13) Wakeham, N. A.; Adams, J. S; Bandler, S. R.; Beaumont, S.; Chang, M. P.; Chervenak, J. A.; Datesman, A. M.; Eckart, M. E.; Finkbeiner, F. M.; Ha, J. Y.; Hummatov, R.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, A. R.; Porter, F. S.; Sadleir, J. E.; Sakai, K.; Smith, S. J.; Wassell, E. J.The measured noise in Mo/Au transition-edge sensor (TES) microcalorimeters produced at NASA has recently been shown to be well described by a two-body electrothermal model with a finite thermal conductance between the X-ray absorber and the TES. In this article, we present observations of a high-frequency peak in the measured current noise in some of these devices. The peak is associated with an oscillatory component of the TES response that is not predicted in a single-body model but can be qualitatively described by the two-body model.Item Josephson Effects in Frequency-Domain Multiplexed TES Microcalorimeters and Bolometers(Springer, 2018-07-03) Gottardi, L.; Smith, Stephen J.; Kozorezov, A.; Akamatsu, H.; van der Kuur, J.; Bandler, S. R.; Bruijn, M. P.; Chervenak, J. A.; Gao, J. R.; den Hartog, R. H.; Jackson, B. D.; Khosropanah, P.; Miniussi, Antoine; Nagayoshi, K.; Ridder, M.; Sadleir, J.; Sakai, Kazuhiro; Wakeham, NicholasFrequency-division multiplexing is the baseline read-out system for large arrays of superconducting transition-edge sensors (TES’s) under development for the X-ray and infrared instruments like X-IFU (Athena) and SAFARI, respectively. In this multiplexing scheme, the sensors are ac-biased at different frequencies from 1 to 5MHz and operate as amplitude modulators. Weak superconductivity is responsible for the complex TES resistive transition, experimentally explored in great detail so far, both with dc- and ac-biased read-out schemes. In this paper, we will review the current status of our understanding of the physics of the TES’s and their interaction with the ac bias circuit. In particular, we will compare the behaviour of the TES nonlinear impedance, across the superconducting transition, for several detector families, namely: high-normal-resistance TiAu TES bolometers, low-normal-resistance MoAu TES microcalorimeters and high-normal-resistance TiAu TES microcalorimeters.Item Long Term Performance Stability of Transition-Edge Sensor Detectors(IEEE, 2023-04-07) Beaumont, Sophie; Adams, J. S.; Bandler, S. R.; Borrelli, R.; Chervenak, J. A.; Cumbee, R.; Finkbeiner, F. M.; Hull, S. V.; Kelley, R. L.; Kilbourne, C. A.; Muramatsu, H.; Porter, F. S.; Sakai, Kazuhiro; Smith, S. J.; Wakeham, Nicholas; Wassell, E. J.; Yoon, S.We are developing superconducting transition-edge sensor (TES) microcalorimeter arrays for a variety of applications such as ground-based laboratory astrophysics experiments and next generation space-based X-ray missions. These detectors can provide X-ray spectral information with an unprecedent resolution of ∼2 eV at 6 keV and have for instance been selected for the X-ray Integral Field Unit (X-IFU) instrument of ESA's large flagship mission Athena. To maintain detector performance over the lifetime of the mission, it is important to understand whether environmental conditions that the detector may be exposed to will affect its properties over time. This “aging” begins right after the array leaves the fabrication environment, with potential exposure to humidity, oxygen, or elevated temperatures which may affect the detector performance. In a few prior arrays we have observed increased fall times in the pulse shape and/or the introduction of anomalous low energy tails on the X-ray spectrum. This is thought to be an indication of “aging” on chips exposed to such conditions, causing e.g., changes in the absorber properties. In this contribution, we report on a systematic characterization of TES properties, before and after exposing the chip to various controlled temperature and humidity levels and assess the changes in the measured transition and pulse shapes, energy resolution, and spectral redistribution.Item Progress in the Development of Frequency‑Domain Multiplexing for the X‑ray Integral Field Unit on Board the Athena Mission(Springer, 2020-01-28) Akamatsu, H.; Gottardi, L.; van der Kuur, J.; de Vries, C. P.; Bruijn, M. P.; Chervenak, J. A.; Kiviranta, M.; van den Linden, A. J.; Jackson, B. D.; Miniussi, Antoine; Ravensberg, K.; Sakai, Kazuhiro; Smith, S. J.; Wakeham, NicholasFrequency-domain multiplexing (FDM) is the baseline readout system for the X-ray Integral Field Unit on board the Athena mission. Under the FDM scheme, TESs are coupled to a passive LC flter and biased with alternating current (AC bias) at MHz frequencies. Using high-quality-factor LC flters and room-temperature electronics developed at SRON and low-noise two-stage SQUID amplifers provided by VTT, we have recently demonstrated good performance with the FDM readout of Mo/Au TES calorimeters with Au/Bi absorbers. We have achieved a performance requested for the demonstration model with the single-pixel AC bias (ΔE = 1.8 eV) and nine-pixel multiplexing (ΔE = 2.6 eV) modes. We have also demonstrated 14-pixel multiplexing with an average energy resolution of 3.3 eV, which is limited by nonfundamental issues related to FDM readout in our laboratory setup.Item Quantum Efficiency Study and Reflectivity Enhancement of Au/Bi Absorbers(Springer Nature Switzerland AG., 2020-03-07) Hummatov, R.; Adams, J. S.; Bandler, S. R.; Barlis, A.; Beaumont, S.; Chang, M. P.; Chervenak, J. A.; Datesman, A. M.; Eckart, M. E.; Finkbeiner, F. M.; Ha, J. Y.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, A. R.; Porter, F. S.; Sadleir, J. E.; Sakai, K.; Smith, S. J.; Wakeham, N.; Wassell, E. J.; Wollack, E. J.X-ray absorbers of the X-ray Integral Field Unit (X-IFU) microcalorimeters are required to provide high quantum efficiency (QE) for incident X-rays and high reflectivity to longer wavelength radiation. The thickness of the electroplated Au and Bi layers of the absorber is tuned to provide the desired pixel heat capacity and the QE. To calculate the QE precisely, in addition to filling factor, we have included the effects of surface roughness, edge profile of the absorbers and the effects of the different angles of incidence of the incoming X-rays from the X-IFU optic. Based on this analysis, it is found that thickness of the Bi layer needs to be adjusted by 4.3% to achieve the X-IFU QE requirements. To enhance the absorber’s rejection of low-energy radiation, a second thin layer of Au is sputter-deposited on top of the Bi layer. Optical measurements in the wavelength range 0.3–20 μm show a significant increase in reflectivity compared to a bare Bi layer.Item Study of Dissipative Losses in AC-Biased Mo/Au Bilayer Transition-Edge Sensors(Springer, 2018-06-26) Sakai, Kazuhiro; Adams, J. S.; Bandler, S. R.; Chervenak, J. A.; Miniussi, Antoine; Smith, S. J.; Wakeham, Nicholas; et alWe are developing kilo-pixel arrays of transition-edge sensors (TESs) for the X-ray Integral Field Unit on ESA’s Athena observatory. Previous measurements of AC biased Mo/Au TESs have highlighted a frequency-dependent loss mechanism that results in broader transitions and worse spectral performance compared to the same devices measured under DC bias. In order to better understand the nature of this loss, we are now studying TES pixels in different geometric configurations. We present measurements on devices of different sizes and with different metal features used for noise mitigation and X-ray absorption. Our results show how the loss mechanism is strongly dependent upon the amount of metal in close proximity to the sensor and can be attributed to induced eddy current coupling to these features. We present a finite element model that successfully reproduces the magnitude and geometry dependence of the losses. Using this model, we present mitigation strategies that should reduce the losses to an acceptable level.Item System performance of a TDM test-bed with long flex harness towards the new X-IFU FPA-DM(2024-03-05) Vaccaro, D.; de Wit, M.; van der Kuur, J.; Gottardi, L.; Ravensberg, K.; Taralli, E.; Adams, J.; Bandler, S. R.; Chervenak, J. A.; Doriese, W. B.; Durkin, M.; Reintsema, C.; Sakai, Kazuhiro; Smith, S. J.; Wakeham, Nicholas; Jackson, B.; Khosropanah, P.; Gao, J. R.; Herder, J. W. A. den; Roelfsema, P.SRON (Netherlands Institute for Space Research) is developing the Focal Plane Assembly (FPA) for Athena X-IFU, whose Demonstration Model (DM) will use for the first time a time domain multiplexing (TDM)-based readout system for the on-board transition-edge sensors (TES). We report on the characterization activities on a TDM setup provided by NASA Goddard Space Flight Center (GSFC) and National Institute for Standards and Technology (NIST) and tested in SRON cryogenic test facilities. The goal of these activities is to study the impact of the longer harness, closer to X-IFU specs, in a different EMI environment and switching from a single-ended to a differential readout scheme. In this contribution we describe the advancement in the debugging of the system in the SRON cryostat, which led to the demonstration of the nominal spectral performance of 2.8 eV at 5.9~keV with 16-row multiplexing, as well as an outlook for the future endeavours for the TDM readout integration on X-IFU's FPA-DM at SRON.Item Thermal fluctuation noise in Mo/Au superconducting transition-edge sensor microcalorimeters(AIP, 2019-04-23) Wakeham, Nicholas; Adams, J. S.; Bandler, S. R.; Beaumont, S.; Chervenak, J. A.; Datesman, A. M.; Eckart, M. E.; Finkbeiner, F. M.; Hummatov, R.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, Antoine; Porter, F. S.; Sadleir, J. E.; Sakai, Kazuhiro; Smith, S. J.; Wassell, E. J.In many superconducting transition-edge sensor (TES) microcalorimeters, the measured electrical noise exceeds theoretical estimates based on a thermal model of a single body thermally connected to a heat bath. Here, we report on noise and complex impedance measurements of a range of designs of TESs made with a Mo/Au bilayer. We have fitted the measured data using a two-body model, where the x-ray absorber and the TES are connected by an internal thermal conductance Gae. We find that the so-called excess noise measured in these devices is consistent with the noise generated from the internal thermal fluctuations between the x-ray absorber and the TES. Our fitted parameters are consistent with the origin of Gae being from the finite thermal conductance of the TES itself. These results suggest that even in these relatively low resistance Mo/Au TESs, the internal thermal conductance of the TES may add significant additional noise and could account for all the measured excess noise. Furthermore, we find that around regions of the superconducting transition with rapidly changing derivative of resistance with respect to temperature, an additional noise mechanism may dominate. These observations may lead to a greater understanding of TES devices and allow the design of TES microcalorimeters with improved performance.