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Joe Fowler: X-ray Fluorescence Line Metrology for the 21st Century
2020-April-23 @ 9:00 am - 10:00 am
Databases of x-ray fluorescence line energies such as those of Deslattes (2003) and Bearden (1967) are critical to the calibration of any analytical tools that identify elemental compositions by their x-ray “fingerprints.” To be useful, such tables have to favor completeness over accuracy. Unfortunately, a full 75% of the lines in the current NIST database (SRD-128) rely on measurements at least 50 years old, coming from an age when the SI meter and the x-ray wavelength had never been tied together. Worse, SRD-128 lacks all information about line shapes or any M lines whatsoever. At NIST, we have begun a program to measure as many lines as possible with transition-edge sensor (TES) microcalorimeters, starting with the hard x-ray L lines of certain lanthanide metals. As Kelsey Morgan described on March 30, a TES combines advantages of solid-state detectors and diffractometers: it measures an enormous spectral region at once with resolving power of 1000 or higher. In tandem, we have also rejuvenated the SI-traceable diffractometer of Deslattes’ team, in order to expand the limited set of lines available for calibration of the TES spectrometer.