High-resolution,energy-dispersive microcalorimeter spectrometer for X-ray microanalysis

We have developed a prototype X-ray microcalorimeter spectrometer with high energy resolution for use in X-ray microanalysis. The microcalorimeter spectrometer system consists of a superconducting transition-edge sensor X-ray microcalorimeter cooled to an operating temperature near 100 mK by a compact adiabatic demagnetization refrigerator, a superconducting quantum interference device current amplifier followed by pulse-shaping amplifiers and pileup rejection circuitry, and a multichannel analyser with computer interface for the real-time acquisition of X-ray spectra. With the spectrometer mounted on a scanning electron microscope, we have achieved an instrument response energy resolution of better than 10 eV full width at half-maximum (FWHM) over a broad energy range at real-time output count rates up to 150 s^?1. Careful analysis of digitized X-ray pulses yields an instrument-response energy resolution of 7.2 ± 0.4 eV FWHM at 5.89 keV for Mn Kα_1,2 X-rays from a radioactive ⁵⁵Fe source, the best reported energy resolution for any energy-dispersive detector.