From Argonne Labs: “The Road to Ultrahigh-Resolution X-ray Spectrometers”

News from Argonne National Laboratory

NOVEMBER 22, 2011
No writer credit

“Two recent developments at the Advanced Photon Source explore paths to routine use of sub-meV x-rays to probe low-energy excitations in matter.
The first is a remarkable experimental demonstration of an x-ray optical scheme that produces x-ray beams with sub-meV linewidths (FWHM) and elimination of the normal Lorentzian tails. The second is a proposal for an alternate optical scheme that may achieve comparable x-ray bandwidths with less demanding optics. “

That’s as far as I am able to go, this stuff is way beyond me. But, maybe it is not way beyond you.

Maybe a couple of images will entice you:

Basic phenomena underlying the AD&AT x-ray optics. In x-ray Bragg diffraction from atomic planes composing nonzero angle η to the crystal entrance face, the crystal acts (a) like an optical prism dispersing the photons into a divergent x-ray fan with photons of different energies E propagating at different reflection angles θ ′ (E) – effect of angular dispersion (AD), (b) as a filter with anomalously high transparency for x rays with incidence angles θ − Ψ in the immediate vicinity (Ψ ≈ 5 µrad) but smaller than the Bragg angle θ – effect of anomalous transmission (AT)

Experimental scheme and combined spectral resolution function of the blue-winged CDFDW monochromator measured against the red-winged CDFDW analyzer. The purple circles show spectral resolution function, the black solid line – spectral functions calculated using multi- crystal dynamical theory of x-ray diffraction. Other functions with the same bandwidth are shown for comparison: green dashed line – Gaussian; dark-red dash-dotted line – Lorentzian.

See the full article here.

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