  Transition Edge Sensor (TES) spectrometers for hard X-ray beamline science
will enable improved X-ray emission and absorption spectroscopy in the
information-rich 2 to 20 keV energy range. We are building a TES-based
instrument for the Advanced Photon Source (APS) synchrotron, to be made
available to beamline users. 24-pixel prototype arrays have recently been
fabricated and tested. The first spectroscopy measurements using these arrays
are promising, with a best single-pixel energy resolution of 11.2 eV and
saturation energy > 20 keV. We present a series of recent X-ray Fluorescence
measurements involving transition metal elements and multi-element samples with
closely spaced emission lines, in particular a Cu-Ni-Co thin film and a foil of
Cu and Hf. The TES-measured spectra are directly compared to spectra measured
with silicon drift detectors at an APS beamline, demonstrating the improved
X-ray science made possible by TES spectrometers.
