HIGH-RESOLUTION SUPERCONDUCTING X-RAY SPECTROMETERS WITH AN ACTIVE AREA OF 282 MU-M X 282 MU-M

Superconducting tunnel junctions coupled to superconducting absorbers may be used as high-resolution, high-efficiency X-ray spectrometers, i re have tested devices with niobium Xray absorbing layers coupled to a luminum layers that serve as quasiparticle traps. In this work we meas ure the current pulses from a large-area tunnel junction using an ampl ifier based on an array of 100 SQUIDs. Using this amplifier and a 282 mu m x 282 mu m junction, we have measured an energy resolution of 19 eV FWHM for 1.5 keV X rays and 21 eV for 2.6 keV X rays. The area of t his junction is eight times area of any junction previously measured t o such high energy resolution.