Phonon-mediated particle detection using superconducting tungsten transition-edge sensors

This thesis describes the development of several superconducting tungsten thin film based particle detector technologies for the detection of dark matter and neutrino scattering events. These technologies also show promise in other applications, including high resolution x-ray spectroscopy.; The detectors described here consist of a superconducting tungsten thin film deposited on a silicon substrate. Phonons from particle interactions in the crystal propagate to the surface where they are absorbed in the tungsten film. The superconducting film is biased at or near its transition temperature. Changes in the resistance of the film are measured.; The most promising technology discussed is a novel sensor in which the temperature of the superconducting W film is held constant within its transition by an electrothermal feedback process. Energy deposited in the film by a particle interaction is removed by a reduction in the feedback Joule heating. The feedback current is measured with a DC SQUID array. This mode of operation leads to substantial improvements in resolution, linearity, dynamic range, and count rate. The fundamental limits on the energy resolution of this detector are analyzed, and found to be below the rms thermodynamic energy fluctuations in the film, and better than any existing technology operating at the same temperature, count rate, and absorber heat capacity. The enhancement of this electrothermal feedback technology with quasiparticle trapping is also explored. In this approach, superconducting Al thin film pads are placed in electrical contact with W lines. When phonons enter the Al film, they create quasiparticles which diffuse into the W lines. Once in the W films they are rapidly thermalized. This enhancement allows the instrumentation of large surface areas with smaller W heat capacity.; An energy resolution of {dollar}<{dollar}400 eV FWHM is measured for 6 keV x-rays interacting on the backside of a 1 cm x 1 cm x 1 mm silicon substrate. The construction of a dark matter detector using this technology will occur this year. Finally, the application of these technologies to other problems, including high resolution x-ray spectroscopy, infrared bolometry, and the resolution of individual low energy ({dollar}{lcub}sim{rcub}{dollar}1 eV) photons is described.