TES spectrometers for advanced x-ray spectroscopy at synchrotrons

In synchrotron-based x-ray spectroscopy, particularly in the photon-in/photon-out mode, diffraction grating spectrometers have played a crucial role thanks to their superior energy resolution. However, they often lack detection efficiency required for measuring weak x-ray signals coming from dilute samples. To overcome this limitation, we have developed TES spectrometers based on an array of transition-edge sensor (TES) microcalorimeters and commissioned two of them at Stanford Synchrotron Radiation Lightsource (SSRL). The SSRL TES spectrometers have a wide spectral coverage of 200—1500 eV, an excellent energy resolution of 1–2 eV FWHM, and a solid angle that is orders of magnitude greater than that of grating spectrometers. This unique combination makes the TES a key instrument for advanced spectroscopy such as RIXS (resonant inelastic x-ray scattering) and REXS (resonant elastic x-ray scattering) with challenging sample environment. In this talk, I will describe the detailed performance of the two TES spectrometers as measured at the synchrotron beamlines and present several science results obtained in synergy between the TES and each beamline's capability. I will also describe our efforts to make the TES spectrometers a more powerful and user-friendly instrument.