HIGH-RESOLUTION ENERGY SPECTROSCOPY AND SUPERCONDUCTIVE TUNNEL JUNCTION

Superconducting Tunnel Junctions are considered for their use as new n uclear radiation detectors with high energy resolution, for radioastro nomy. In fact they have potentiality for 0.05% resolution, more than o ne order of magnitude better than conventional detectors. The reasons and the advantages of using this tunnel junctions are briefly introduc ed. A description of the working principle and the basic experimental set up are also outlined. The attention is focused on Nb/AlOx/Nb junct ion which is presently the state of art of superconductive tunnel junc tion technology with respect to stability and cyclability. Junctions w ith high dynamical resistance in the biasing region are in fact necess ary to optimize the signal to noise ratio and then improve the high en ergy resolution. The characterization at low temperatures (down to 1.2 K) of samples fabricated with a special <<island>> geometry is presen ted to demonstrate the feasibility of their use because they satisfy t he rather stringent quality requirements. Finally, preliminary results concerning the junction responsivity to nuclear radiation at relative ly high temperature (T=1.5 K) are reported. Although the obtained reso lution of 700 eV with 6 keV X-rays is far from the theoretical limit, better results can be expected working with the devices at lower tempe ratures and improving the structure configuration.