Soft X-ray performance of superconducting tunnel junction arrays

A number of 6x6 element arrays of Ta-based superconducting tunnel junctions have been manufactured for photon counting applications with moderate ener gy resolution in ground-based optical astronomy, The individual array eleme nts shaw low leakage, uniform responsivity across the array, good simultane ous Josephson current suppression and minor crosstalk between adjacent pixe ls. The same arrays have been characterized in the soft ii-ray range (E=270 -1500 eV). The base electrode response shows good energy resolving power (E /Delta E approximate to 140). Unwanted spectral features originating from o ther parts of the detector can be largely eliminated by risetime filtering. Modifications in the layering are necessary in order to improve the soft i i-ray detection efficiency.