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==History==
The first demonstrations of the superconducting transition's measurement potential appeared in the 1940s, thirty years after [[Heike Kamerlingh Onnes|Onnes]]'s discovery of [[superconductivity]]. D.H. Andrews demonstrated the first transition-edge [[bolometer]], a current-biased [[tantalum]] wire which he used to measure an infrared signal. Subsequently he demonstrated a transition-edge [[Calorimeter (particle physics)|calorimeter]] made of [[niobium nitride]] which was used to measure [[alpha particles]].<ref>D.H. Andrews ''et al.'', "Attenuated superconductors I. For measuring infra-red radiation." ''Rev. Sci. Instrum.'', '''13''', 281 (1942), {{doi|10.1063/1.1770037}}</ref> However, the TES detector did not gain popularity for about 50 years, due primarily to the difficulty of signal readout from such a low-[[Electrical impedance|impedance]] system. A second obstacle to the adoption of TES detectors was in achieving stable operation in the narrow superconducting transition region. [[Joule heating]] in a current-biased TES can lead to thermal runaway that drives the detector into the normal (non-superconducting) state, a phenomenon known as positive [[electrothermal feedback]]. The thermal runaway problem was solved in 1995 by K. D. Irwin by voltage biasing the TES, establishing stable negative [[electrothermal feedback]], and coupling them to superconducting quantum interference devices ([[SQUID]]) current amplifiers
==Setup, operation, and readout==
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===Thermometer===
The TES operates as a thermometer in the following manner: absorbed incident energy increases the resistance of the voltage-biased sensor within its transition region, and the integral of the resulting drop in current is proportional to the energy absorbed by the detector.<ref name=NIST2/> The output signal is proportional to the temperature change of the absorber, and thus for maximal sensitivity, a TES should have low heat capacity and a narrow transition. Important TES properties including not only heat capacity but also thermal conductance are strongly temperature dependent, so the choice of [[Superconductivity#
===Thermal conductance===
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==Advantages and disadvantages==
TES detectors are attractive to the scientific community for a variety of reasons. Among their most striking attributes are an unprecedented high detection efficiency customizable to wavelengths from the millimeter regime to gamma rays,<ref name=IrwinHilton /><ref name=NIST /> and a theoretical negligible background dark count level (less than 1 event in 1000 s from intrinsic [[Phonon noise|thermal fluctuations]] of the device<ref name=NIST2 />). (In practice, although only a real energy signal will create a current pulse, a nonzero background level may be registered by the counting algorithm or the presence of background light in the experimental setup. Even thermal [[blackbody radiation]] may be seen by a TES optimized for use in the visible regime.)
TES single-photon detectors suffer nonetheless from a few disadvantages as compared to their [[Single-photon avalanche diode|avalanche photodiode]] (APD) counterparts. APDs are manufactured in small modules which count photons out-of-the-box with a [[dead time]] of a few nanoseconds and output a TTL pulse corresponding to each photon with a jitter of tens of picoseconds. In contrast, TES detectors must be operated in a cryogenic environment, output a signal which must be further analyzed to identify photons, and have a jitter of approximately 100 ns.<ref name=NIST /> Furthermore, a single photon spike on a TES detector lasts on the order of microseconds.
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==See also==
{{
*[[Bolometer]]
*[[Cryogenic particle detectors]]
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