Characterization of superconducting tunnel junction X-ray detectors by means of monochromatized undulator radiation

A superconducting tunnel junction X-ray detector system was designed to match current energy resolution, count rate and UHV requirements in soft X-ray spectroscopy. It employs a two-stage adiabatic demagnetization refrigerator with a 23 cm long cold finger to operate the detector inside a sample chamber for X-ray fluorescence measurements. This cryogenic detector system was characterized in the energy range from 100 eV to 900 eV with respect to its energy resolution ranging from 12 eV to 25 eV FWHM, count rate capability up to 80 kcps and absolute detection efficiency using undulator radiation monochromatized by means of a plane grating monochromator beamline. Collimating the beam to the detector area improves the energy resolution by about 10%. The potential of this novel detector for beamline characterization was investigated.