Superconducting transition-edge-microcalorimeter X-ray spectrometer with 2 eV energy resolution at 1.5 keV

We describe the operation and performance of a prototype microcalorimeter “energy-dispersive” (non-dispersive) X-ray spectrometer (μcal EDS) developed at NIST for use in X-ray microanalysis and X-ray astronomy. The low-energy microcalorimeter detector, consisting of an Al–Ag bilayer superconducting transition-edge sensor (TES) in thermal contact with a Bi X-ray absorber, is designed for operation in the energy range from 0–2 keV and is fabricated using a shadow-mask lithographic process. The TES microcalorimeter is cooled by a compact adiabatic demagnetization refrigerator and is mounted on a scanning electron microscope. This device achieves a best energy resolution of 2.0±0.1 eV at 1.5 keV, as determined from the analysis of digitized X-ray spectra of a complex glass containing many elements.