Quantitative Analysis with the Transition Edge Sensor Microcalorimeter X-ray Detector

The use of a microcalorimeter X-ray detector with a transition edge sensor in an electron probe to perform quantitative analysis is reported. Two bulk samples of multielement glasses that have been previously characterized by chemical methods for use as standard reference materials were analyzed. The spectra were analyzed against standards using three different correction schemes. In one of the standards, the reference line was easily resolved despite its proximity within 45 eV of another line. With the exception of direct measurements of oxygen (a particularly challenging element), the results are in agreement with the certified characterization to better than 1% absolute or 8% relative. This demonstrates the potential of microcalorimeter detectors as replacements for conventional energy dispersive detectors in applications requiring high energy resolution. INTRODUCTION Microcalorimeter X-ray detectors represent a new technology that achieves high energy resolution over a large energy range [1,2]. They make it possible to resolve individual lines of a broad range of elements that would have interfered in earlier detectors. Previous studies have concentrated on the resolution [3] and stability [4] of the microcalorimeter detectors as a precondition for use in actual analyses. There are further questions regarding the counting rates, the times required to obtain statistically significant spectra, and the suitability of the detector for use with electron microscopes and microprobes [5,6]. We address these concerns by reporting on quantitative analyses that we have carried on non-stoichiometric materials with a microcalorimeter detector employing a transition edge sensor (TES) as the thermally sensitive element [7]. The analyses were performed on an electron beam probe. The samples consisted of bulk glasses that were previously characterized by chemical analysis and certified as NIST Standard Reference Materials. DESCRIPTION OF THE EXPERIMENTAL PROCEDURE The NIST-designed microcalorimeter detector that we used in this investigation is similar to one that has been previously described [4]. It consists of an X-ray absorbing element that is isolated except for contact with a thermal reservoir held at 70 mK. Sudden temperature increases caused by the absorption of individual X-ray photons are registered by the TES, a thin film of superconductor maintained in the middle of its superconducting-normal transition by a dc current. The changes in the resistance of the film in response to the temperature pulses determine 51 Copyright ©JCPDS-International Centre for Diffraction Data 2007 ISSN 1097-0002