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[[File:NIST Tungsten Transition Edge Sensor.png|thumb|alt=Image of four tungsten transition
A '''transition
==History==
The first demonstrations of the superconducting transition's measurement potential appeared in the 1940s, 30 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
==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#Superconducting phase transition|transition temperature]] ''T''<sub>c</sub> is critical to the device design. Furthermore, ''T''<sub>c</sub> should be chosen to accommodate the available [[cryostat|cryogenic system]]. Tungsten has been a popular choice for elemental TESs as thin-film tungsten displays two phases, one with ''T''<sub>c</sub> ~15
===Thermal conductance===
Finally, it is necessary to tune the [[Thermal conductivity|thermal coupling]] between the TES and the bath of cooling liquid; a low thermal conductance is necessary to ensure that incident energy is seen by the TES rather than being lost directly to the bath. However, the thermal link must not be too weak, as it is necessary to cool the TES back to bath temperature after the energy has been absorbed. Two approaches to control the thermal link are by electron–phonon coupling and by mechanical machining. At cryogenic temperatures, the [[electron]] and [[phonon]] systems in a material can become only weakly coupled. The electron–phonon thermal conductance is strongly temperature-dependent, and hence the thermal conductance can be tuned by adjusting ''T''<sub>c</sub>.<ref name=IrwinHilton /><ref name=NIST /> Other devices use mechanical means of controlling the thermal conductance such as building the TES on a sub-micrometre membrane over a hole in the substrate or in the middle of a sparse "spiderweb" structure.<ref>J. Bock ''et al.'', "A novel bolometer for infrared and millimeter-wave astrophysics", ''Space Science Reviews'', '''74''', 229–235 (1995), {{doi|10.1007/BF00751274}}.</ref>
==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
==Applications==
TES arrays are becoming increasingly common in physics and astronomy experiments such as [[James Clerk Maxwell Telescope#SCUBA-2|SCUBA-2]], the HAWC+ instrument on the [[Stratospheric Observatory for Infrared Astronomy]], the [[Atacama Cosmology Telescope]], the [[Cryogenic Dark Matter Search]], the [[Cryogenic Observatory for Signatures Seen in Next-Generation Underground Searches]], the [[Cryogenic Rare Event Search with Superconducting Thermometers]], [[the E and B Experiment]], the [[South Pole Telescope]],
==See also==
{{commons category|Transition edge sensor}}
* [[Bolometer]]
* [[Cryogenic particle detectors]]
==References==
{{reflist}}
[[Category:Superconducting detectors]]
[[Category:Radiometry]]
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