AlMn Transition Edge Sensors for Advanced ACTPol
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Advanced ACTPol (AdvACT) will use an array of multichroic polarization-sensitive AlMn transition edge sensor (TES) bolometers read out through time-division multiplexing. Aluminum doped with a low concentration of manganese can be deposited to a bulk film thickness for a more reliable superconducting critical temperature uniformity compared to thin bilayers. To build the TES, the AlMn alloy is deposited, over Nb wiring, to a specific thickness to set the TES normal resistance. The doping concentration of manganese coarsely defines the TES critical temperature, while a fine tuning is achieved by heating the deposited film to a specific temperature. The TES island is connected to the thermal bath via four silicon-nitride membranes, where their geometry defines the thermal conductance to the temperature of the bath. Lastly, the TES heat capacity is increased by addition of PdAu electrically connected to the AlMn film. Designs and performance characteristics of these AlMn TESs are presented for use in AdvACT.
KeywordsTransition edge sensor AlMn Bolometer Thin film Superconductor Microfabrication Heating Critical temperature
This work was supported by the U.S. National Science Foundation through awards 1312380 and 1440226. The NIST authors would like to acknowledge the support of the NIST Quantum Initiative. The development of multichroic detectors and lenses was supported by NASA Grants NNX13AE56G and NNX14AB58G. The work of BJK, BLS, JTW, and SMS was supported by NASA Space Technology Research Fellowship awards.
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