Prospects for dark matter detection with a large superconducting niobium absorber

The search for weakly interacting massive particles (WIMPs) by observing their scattering in underground detectors will require a range of target materials, for which niobium is a good candidate. α-particles, γ-rays and neutrons were detected in single crystals of superconducting niobium of masses 2 and 12 g. The nonequilibrium phonon and quasiparticle states arising from particle interactions were observed at crystal surfaces using aluminium superconducting tunnel junctions. 5.5 MeV α-particle interactions were observed in the 12 g crystal with an energy resolution of 170 keV FWHM and a position resolution of better than 500 μm. Position dependent signals were also detected arising from α-particles, γ-rays and neutrons in 2 g crystals. (R.P.) 10 refs.; 10 figs