Vacuum formed temporary spherically and toroidally bent crystal analyzers for x-ray absorption and x-ray emission spectroscopy

Abstract

We demonstrate that vacuum forming of 10-cm diameter silicon wafers of various crystallographic orientations under an x-ray permeable, flexible window can easily generate spherically bent crystal analyzers (SBCA) and toroidally bent crystal analyzers (TBCA) with ~1-eV energy resolution and a 1-m major radius of curvature. In applications at synchrotron light sources, x-ray free electron lasers, and laboratory spectrometers these characteristics are generally sufficient for many x-ray absorption fine structure (XAFS), x-ray emission spectroscopy (XES), and resonant inelastic x-ray scattering (RIXS) applications in the chemical sciences. Unlike existing optics manufacturing methods using epoxy or anodic bonding, vacuum forming without adhesive is temporary in the sense that the bent wafer can be removed when vacuum is released and exchanged for a different orientation wafer. Therefore, the combination of an x-ray compatible vacuum-forming chamber, a library of thin wafers, and a small number of forms having different secondary curvatures can give extreme flexibility in spectrometer energy range. As proof of this method we determine the energy resolution and reflectivity for several such vacuum-formed bent crystal analyzers (VF-BCA) in laboratory based XAFS and XES studies using a conventional x-ray tube. For completeness we also show x-ray images collected on the detector plane to characterize the resulting focal spots and optical aberrations.(*) seidler@uw.edu ( §) These authors contributed equally to this work.

An improved laboratory-based x-ray absorption fine structure and x-ray emission spectrometer for analytical applications in materials chemistry research

“…The decline in count rates observed in Figure 4 is consistent with ray tracing simulations reported elsewhere. 41 If a larger detector or toroidal optic is integrated into the design, consistent count rates could be observed across the instrument's angular range. 41 The spectrometer's reliability was assessed according to its scan-to-scan reproducibility.…”

“…As 𝜃 𝐵 deviates strongly from backscatter (decreasing B) the height of the refocused beam on the detector quickly becomes taller than the active height of the detector, resulting in significant inefficiency. As discussed below, and in more detail in an upcoming manuscript, 41 this can be ameliorated by incorporation of a taller SDD or by use of a toroidal curved crystal analyzer that is tailored to the Bragg angle range of interest.…”

The versatile X-ray beamline of the Munich Compact Light Source: design, instrumentation and applications

“…Recently, data acquisition times as short as 1 min have been successfully demonstrated at a quality comparable with synchrotrons (Huang et al, 2020). Other laboratory XAS setups, based on X-ray tubes (Seidler et al, 2014;Né meth et al, 2016;Bè s et al, 2018;Błachucki et al, 2019;Jahrman et al, 2019), laser-plasma sources (Uhlig et al, 2013), laser-betatron ones (Mahieu et al, 2018) or high harmonic generation (Pertot et al, 2017;Popmintchev et al, 2018) typically operate at a lower X-ray energy below 10 keV and typically require exposure times of tens of minutes to hours. This elongated acquisition time originates from the lower brilliance of X-ray tubes compared with ICSs, like at the MuCLS.…”

General method to calculate the elastic deformation and X-ray diffraction properties of bent crystal wafers

“…Notwithstanding, TBCAs are encountered rarely as they are more difficult to manufacture than SBCAs and need to be tuned for a specific Bragg angle which incurs increased expenses, especially if the spectrometer setup is meant to be used for a wide range of photon energies. However, at least some of these problems can be avoided by using vacuum-forming optics (Jahrman et al, 2019a) to apply the toroidal bending to a flat wafer temporarily and, perhaps with further development, dynamically in the course of an experiment.…”