A prototype weakly interacting massive particle (WIMP) detector system is described. The detection efficiency is much larger when the incident neutral particle flux is perpendicular to the detector plane than when it is parallel to the plane. A greatly scaled-up system based on this device would therefore be sensitive to the diurnal rotation of the "WIMP wind" produced by the solar system's rapid motion through the galactic halo. Experimental results are reported which exhibit the detection efficiency anisotropy when neutrons were used to simulate the interactions of WIMPS.

As a part of continuing development of thin film Ge1−xAux thermistors for ultralow mass highly sensitive cryogenic phonon sensors, the ac responsivity and hot electron effects have been explored. Responsivity as high as 1.6 nV/eV was achieved at 20 mK. A derivation is presented for the power index β=6 for electron-phonon heat exchange in variable range hopping conductivity. Applying our previously developed optimization theory for bias-assisted tunneling, hot electron effects and bias-assisted tunneling were shown to account equally well for the nonlinear dc current–voltage characteristic. However, a model was developed for the thermal time constants of these devices which does predict a clear distinction between bias-assisted tunneling and the hot electron effects. Comparison of data with this model showed that bias-assisted tunneling rather than hot electron effects was the dominant finite-bias effect in the Ge1−xAux thin films.

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