This is an RUI renewal request for research aimed at the development of detectors sufficiently sensitive to be used in a search for "dark matter." Such matter's existence is strongly suggested by a number of astrophysical measurements. It interacts gravitationally, but eludes direct observation. It may consist of weakly interacting, non-baryonic elementary particles such as neutrinos or other species predicted by grand unified theories. Detectors of such particles require much lower threshold of sensitivity and larger cross section than offered by conventional devices. The PI, in collaboration with Dr. B. Cabrera of Stanford U. and Dr. C. J. Martoff of Temple University has proposed the development of a "silicon crystal acoustic detector (SiCAD)" which senses ballistic phonons generated by the collision of incident particles with a nucleus or electron in a cube of ultra pure single-crystal silicon cooled below 0.1K. The present proposal focusses upon her efforts to develop extremely sensitive superconducting tunnel junctions as phonon sensors, and uses modern integrated circuit fabrication techniques, many of which were developed locally in her S.F. State laboratory during the first three year grant.
