A new detector of nuclear radiation based on ballistic phonon propagation in single crystals at low temperatures

Abstract The absorption of 5.5 MeV α -particles in a silicon single crystal kept at T =0.38 K was detected by an array of superconducting tunnel diodes evaporated onto the surface of the crystal. Signals were mediated by phonons propagating ballistically within the crystal. The phon flux proved anisotropic due to phonon focusing effects. This anisotropy and the study of time resolved signal correlations between the diodes allowed us to distinguish two spots of α -absorption separated by 0.75 mm. This detection principle might be applicable in a variety of experiments in nuclear and elementary particle physics.