Transition-edge sensor: Difference between revisions

Revision as of 16:48, 12 April 2012

Revision as of 17:14, 12 April 2012

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==History==

The first demonstrations of the superconducting transition's measurement potential appeared in the 1940's, thirty years after Onnes's discovery of [[superconductivity|superconductivity]]. D.H. Andrews demonstrated first a transition-edge [[bolometer|bolometer]], a current-biased tantalum wire which he used to measure an infrared signal, and thereafter a transition edge [[calorimeter|calorimeter]], made of niobium nitride and used to measure alpha-particles. <ref> D.H. Andrews et. al.m "Attenuated Superconductors i. For Measuring Infra-Red Radiation." Rev. Sci. Instrum., 13, 281 (1942).</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-impedance system. A second obstacle to the adoption of TES detectors was in optimizing stable operation in the narrow transition edge. [[Joule heating|Joule heating]] in a current-biased TES can lead to thermal runaway that drives the detector normal-conducting. A solution to the readout problem has been found in superconducting quantum interference devices ([[SQUID|SQUIDs]]) which are now designed to pair effectively with the TES detectors; the additional development of voltage-biased operation for TESs has facilitated wide-spread adoption of TES detectors since the late 1990's.<ref name="IrwinHilton">K. D. Irwin and G. C. Hilton, "Transition-Edge Sensors," ''Cryogenic Particle Detection'', ed. C. Enss, Springer, 2005, [http://dx.doi.org/10.1007/10933596_3 {{doi:|10.1007/10933596_3]}}</ref>

==Setup, Operation, and Readout==

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===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|tungsten]] TES as its own absorber, thereby absorbing up to 20% of the input 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).[http://people.bu.edu/alexserg/APL_2003.pdf DOI:] {{doi|10.1063/1.1596723]}}</ref> If high-efficiency detection is desired, the TES may be fabricated in a multi-layer [[Optical_cavity|optical cavity]] tuned to the desired operating wavelength and employing a backside mirror and frontside anti-reflection coating. Such tricks can decrease the transmission and reflection from the detectors to negligibly low values, resulting in a device with a device whose efficiency in principle exceeds 99%. (In fact, 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|Bismuth]] film is often employed.<ref name=IrwinHilton /> Any absorber should have low [[heat_capacity|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 are varied and complicated, including resonant cavities as described above, [[feedhorn|feedhorns]], and more.<ref name=IrwinHilton />

=== Thermometer ===