HIGH-RESOLUTION X-RAY-SPECTRA MEASURED USING TANTALUM SUPERCONDUCTINGTUNNEL-JUNCTIONS

The spectral response of a 100x100 mu m(2) tantalum based superconduct ing tunnel junction to 5.9 keV x-ray photons from a Fe-55 source has b een studied. In full illumination the energy resolution for the Mn K-a lpha line complex is 56 eV, dominated by spatial nonuniformity in the response of the detector. When illuminating selectively a 5-10 mu m di am spot in the center of the detector, the energy resolution improves to 22 eV, corresponding to 15.7 eV for the individual Mn K-alpha 1 and Mn K-alpha 2 lines. This exceeds the predicted theoretical energy res olution of 7.3 eV for this type of device by only a factor of similar to 2. (C) 1998 American Institute of Physics. [S0003-6951(98)00125-9].