Shot Noise Measurements in Diffusive Normal Metal - Superconductor (N-S) Junctions

We report on the measurements of non-equilibrium noise in diffusive normal metal - superconductor (N-S) junctions. We observe that at bias voltages less than the gap voltage the shot noise is doubled compared to the normal diffusive conductor, in agreement with theoretical predictions. We also observe that the crossover from the thermal to shot noise occurs at bias voltages smaller than for the normal conductor, in qualitative agreement with theory.