A SUPERCONDUCTING X-RAY SPECTROMETER WITH A TANTALUM ABSORBER AND LATERAL TRAPPING

We report the development of Nb-Ta-Al-Al2O3-Al superconducting tunnel junction structures for high energy resolution and high efficiency X-r ay detection, These devices utilize a Ta X-ray absorber with supercond uctor ''bandgap engineered'' quasiparticle trapping to improve charge collection, Experimental results at 0.3 K are presented, showing energ y resolution of 102 eV full-width-half-maximum for 6 keV X-rays, Colle cted charge is in excess of 5 x 10(6) electrons. The absorption effici ency is better than 35%; Devices thermally cycle with no change in cha racteristics.