An X-ray photon-counting imaging spectrometer based on a Ta absorber with four superconducting tunnel junctions

We present the first results obtained with a two-dimensional X-ray imaging spectrometer consisting of a 200 x 200 mu m(2) Ta absorber and read out by four Ta/Al superconducting tunnel junctions (STJs). A preliminary image reconstruction algorithm allows the visualisation of the diffraction pattern from a 5 mu m pinhole illuminated with 10 keV X-rays. The image suggests a spatial resolution better than 10 mu m The algorithm does not take into account quasi-particle losses in the absorber. Hence, the pulse-height reconstruction is not optimal and the energy resolution varies significantly across the absorber. The best energy resolution is obtained for a 20 x 20 mu m(2) area in the centre of the absorber. and amounts to similar to 77 eV at a photon energy of 5895 eV, with a 70 eV electronic noise contribution, (C) 2000 Elsevier Science B.V. All rights reserved.