A self-biasing cryogenic particle detector utilizing electrothermal feedback and a SQUID readout

We are developing and testing a new type of superconducting transition edge sensor for phonon mediated particle detection. This sensor consists of a superconducting tungsten thin film deposited on a silicon substrate. The temperature of the film is held constant within the superconducting transition (T/sub c//spl ap/70 mK) by an electrothermal feedback process, while the substrate temperature is well below the film temperature. Phonon energy deposited in the film is removed by a reduction in feedback Joule heating, which is measured using a series array of DC SQUIDs. The resulting signals show improvements in linearity and signal to noise ratio over our previous transition edge sensors.<>