A four-point crystal bender for dispersive X-ray absorption spectroscopy

Abstract

A new crystal bender for dispersive X-ray absorption fine-structure spectroscopy (XAFS) has been built and its performance characterized. The bender employs an adjustable four-point bending mechanism and a contoured crystal, which makes it possible to produce an excellent approximation of the ideal elliptical bend from 8000 to 20000 eV with a single such Si (220) crystal. With the near-elliptical optics, it is possible to achieve a focus size of 175 lam with a 5 mm source and simultaneously to achieve a useful bandpass of 700 at 9000, 1200 at 11 500 and 2000 eV at 18 000 eV. The upper limit on the resolution, which is dictated by the finite source size in this configuration, is 2-5 eV for all of the energy ranges studied.

High-quality energy-dispersive XAFS on the 1 s timescale applied to electrochemical and catalyst systems

“…The 4-point bender gets around these problems by using a rectangular crystal to which a separate couple can be applied at each end. It is effectively a mirror bender mechanism on its side, (see figure 1) and in principle it is similar to those of Hagelstein M. et al 1996, Allen P.G. et al 1993, Lee P.L.…”

Liquid-metal-cooled curved-crystal monochromator for Advanced Photon Source bending-magnet beamline 1-BM

“…Method (iv) can in principle provide a very nearly elliptical shape and a very small focal spot size for a range of energies, though this remains to be demonstrated. 15 Also, for typical values of p and q on the 1-BM beamline, the proposed corrections to a rectangular crystal shape 15 are very small. For our application, we have selected method (iii) because a single crystal, of simple shape, should provide a sufficiently small focal spot over a wide energy range.…”

Quick extended x-ray absorption fine structure instrument with millisecond time scale, optimized for in situ applications

“…In energy dispersive EXAFS ͑EDE͒ one can take the snapshots of the samples at a time scale of few milliseconds. [1][2][3][4][5] EDE can be efficiently used in transmission mode only, and is thus limited to the cases when the samples are concentrated and very uniform in thickness. Detector normalization problems, temporal changes in beam flux, and spatial beam stability can decrease data quality.…”