ADVANCES IN STANFORD PHONON-MEDIATED ELEMENTARY PARTICLE DETECTORS

We have demonstrated a new phonon sensor design based on aluminum phon on collection pads connected to tungsten transition-edge sensors (TES) . The device is patterned onto a silicon crystal and phonons produced by events in the Si are absorbed into the aluminum films where about h alf of the energy is converted into long-lived quasiparticle excitatio ns. These diffuse until they encounter the lower gap W regions where t hey deposit their potential energy to the electron system in the W. Wi th the Si crystal at similar to 40 mK, the W is kept near the center o f its resistive transition (similar to 90 mK) using voltage bias and J oule self-heating. Current changes induced by particle events are meas ured with a high-bandwidth SQUID amplifier readout. We have demonstrat ed an energy resolution of similar to 360 eV FWHM and a position sensi tivity of similar to 0.2 mm for Fe-55 X-rays. We have also completed a new analysis of the nuclear recoil versus electron recoil ballistic p honon production experiments which used our earlier generation Ti TES on Si crystals, The new results set an upper limit on the distinction between the two phonon spectra and provide a better understanding of t he phonon sensor response.