SQUID based W-Al quasiparticle trapping assisted transition edge sensor

We have demonstrated a new type of phonon sensor for cryogenic particle detectors with a high-bandwidth SQUID readout. Our Quasiparticle trapping assisted Electrothermal feedback Transition edge sensor (QET) utilizes aluminum quasiparticle traps attached to a tungsten superconducting transition edge sensor patterned on a silicon substrate. The tungsten lines are voltage biased and self-regulate in the transition region. We have tested three versions of these detectors. One detector consisted of four QET sensors patterned on the surface of a 1 cm x 1 cm x 1 mm silicon substrate. With this detector, we have shown an energy resolution of similar to 400 eV FWHM and position sensitivity of similar to 0.3 mm for 6 keV X-rays from an Fe-55 source. We tested a second detector identical to the first but with the addition of an ionization sensor. With information from the ionization channel, we were able to distinguish electron-recoil events from nuclear-recoil events. Most recently, we have tested a 2 cm x 2 cm x 2 mm detector with four QET sensors.