Content deleted Content added
m →Functionality: fmt., punct., style |
Link suggestions feature: 3 links added. |
||
| (17 intermediate revisions by 9 users not shown) | |||
Line 1:
[[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==
Line 13:
===Absorber===
The simplest absorption scheme can be applied to TESs operating in the near-IR, optical, and UV regimes. These devices generally utilize a [[tungsten]] TES as its own absorber, which absorbs up to 20% of the incident radiation.<ref name = NIST2>A. J. Miller ''et al.'', "Demonstration of a low-noise near-infrared photon counter with multiphoton discrimination", ''Appl. Phys. Lett.'', '''83''', 791–793. (2003), {{doi|10.1063/1.1596723}}.</ref> If high-efficiency detection is desired, the TES may be fabricated in a multi-layer [[optical cavity]] tuned to the desired operating wavelength and employing a backside mirror and frontside anti-reflection coating. Such techniques can decrease the transmission and reflection from the detectors to negligibly low values; 95% detection efficiency has been observed.<ref name=NIST/> At higher energies, the primary obstacle to absorption is transmission, not reflection, and thus an absorber with high photon stopping power and low heat capacity is desirable; a [[bismuth]] film is often employed.<ref name=IrwinHilton/> Any absorber should have low [[heat capacity]] with respect to the TES. Higher heat capacity in the absorber will contribute to noise and decrease the sensitivity of the detector (since a given absorbed energy will not produce as large of a change in TES resistance). For far-IR radiation into the millimeter range, the absorption schemes commonly employ [[Antenna (radio)|antennas]] or [[feedhorn]]s.<ref name=IrwinHilton />
===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
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]]
| |||