High-Energy-Resolution Microcalorimeter Spectrometer for EDS X-ray Micro Analysis

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Si(Li) and Ge Energy Dispersive Spectroscopy (EDS) detectors are commonly used for x-ray microanalysis because they are easy to use, inexpensive to operate, and offer both rapid qualitative evaluation of chemical composition and accurate quantitative analysis. Unfortunately, they are limited by energy resolutions on the order of 100 eV, which is insufficient to resolve many important overlapping x-ray peaks in materials of industrial interest, such as the Si Kα and W Mα peak overlap in WSi₂. Although WDS spectrometers with excellent energy resolution (typically 2 eV to 10 eV) can resolve most peak overlaps, qualitative WDS analysis is limited by the need to serially scan over the entire energy range using multiple diffraction crystals. There is a need for a new generation of x-ray spectrometers for microanalysis that combines the excellent energy resolution of WDS spectrometers with the ease of use and the parallel energy detection capability of EDS spectrometers.

We are developing a high-energy-resolution x-ray microcalorimeter spectrometer for use in x-ray microanalysis. Our microcalorimeter spectrometer consists of a superconducting transition-edge microcalorimeter cooled to an operating temperature of 100 mK by a compact adiabatic demagnetization refrigerator mounted on a SEM column, read-out SQUID (Superconducting Quantum Interference Device) electronics followed by pulse-shaping amplifiers and pile-up rejection circuitry, and a multichannel analyzer with real-time computer interface.