Effects of Normal Metal Features on Superconducting Transition-Edge Sensors

Wakeham, N.; Adams, J. S.; Bandler, S. R.; Chervenak, James A.; Datesman, A.; Eckart, Megan E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.; Miniussi, Antoine R.; Porter, F. S.; Sadleir, J. E.; Sakai, Kazuhiro; Smith, S. J.; Wassell, E. J.; Yoon, Won-Sik

doi:10.1007/s10909-018-1898-z

Cited by 25 publications

(36 citation statements)

References 11 publications

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“…Then they suddenly increase, forming a peak around the high part of the transition to end up eventually with very low values when the TES becomes normal. Such a peak has already been observed in other work [35,36] and looks consistent with the presence of metal bars. Moreover, a different alignment between these bars and the detector can induce a shifting of this peak [37].…”

Section: Resultssupporting

confidence: 90%

Complex impedance of TESs under AC bias using FDM readout system

et al. 2019

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The next generation of Far-infrared and X-ray space observatories will require detector arrays with thousands of transition edge sensor (TES) pixel. It is extremely important to have a tool that is able to characterize all the pixels and that can give a clear picture of the performance of the devices. In particular, we refer to those aspects that can affect the global energy resolution of the array: logarithmic resistance sensitivity with respect to temperature and current ( and  parameters, respectively), uniformity of the TESs and the correct understanding of the detector thermal model. Complex impedance measurement of a TES is the only technique that can give all this information at once, but it has been established only for a single pixel under DC bias. We have developed a complex impedance measurement method for TESs that are AC biased since we are using a MHz frequency domain multiplexing (FDM) system to readout an array. The FDM readout demands for some modifications to the complex-impedance technique and extra considerations, e.g. how to modulate a small fraction of the bias carrier frequencies in order to get a proper excitation current through the TESs and how to perform an accurate demodulation and recombination of the output signals. Also, it requires careful calibration to remove the presence of parasitic impedances in the entire readout system. We perform a complete set of AC impedance measurements for different X-ray TES microcalorimeters based on superconducting TiAu bilayers with or without normal metal Au bar structures. We discuss the statistical analysis of the residual between impedance data and fitting model to determine the proper calorimeter thermal model for our detectors. Extracted parameters are used to improve our understanding of the differences and capabilities among the detectors and additionally the quality of the array. Moreover, we use the results to compare the calculated noise spectra with the measured data. I. INTRODUCTION Transition edge sensor (TES) microcalorimeters [1] are very versatile superconducting devices, which can be used to detect radiation in a wide energy range e.g. from -ray down to submillimeter [2-8]. A TES consists of a superconducting thin film, typically with a transition temperature Tc100 mK, which is strongly coupled to its absorber but weakly thermal coupled to a lower temperature heat bath via a thermal conductance G. In principle, TESs operate as thermometers: the absorption of incident photons by means of the absorber heats the device, which is biased in the transition between the superconducting and the normal states, causing a change in the resistance that is proportional to the photon energy absorbed. This variation is read out using a superconducting quantum interference device (SQUID).

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Section: Resultssupporting

confidence: 90%

Complex impedance of TESs under AC bias using FDM readout system

et al. 2019

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“…The TES size and the normal metal structure used to suppress the excess noise in microcalorimeters contribute as well in shaping the TES resistive transition [4,5]. The physical processes in the TES are then more complicated than the ideal case considered here [9,16] and a better understanding of those processes is essential to further optimize the detectors both in the dc and ac bias configuration.…”

Section: Resultsmentioning

confidence: 99%

Josephson Effects in Frequency-Domain Multiplexed TES Microcalorimeters and Bolometers

et al. 2018

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Josephson Effects in Frequency-Domain Multiplexed TES Microcalorimeters and Bolometers Gottardi, L.; Smith, S. J.; Kozorezov, A.; Akamatsu, H.; Bruijn, M. P.; Chervenak, J. A.; Gao, J. R.; Jackson, B. D.; Ridder, M.; More AuthorsAbstract Frequency-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 5 MHz 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.

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“…Moreover, bare TESs (i.e. without normal metal stripes which were originally introduced to suppress the so-called excess-noise) have shown less weak-link effect and a smooth transition curve [6]. Taking these into account, new TES design rules have emerged as: low square resistance with a thick bi-layer, moderately high ohmic resistance enabled by changing the aspect ratio and no metal strips.…”

Section: K Nagayoshi • ML Ridder • Mp Bruijn • L Gottardi • E mentioning

confidence: 99%