High Energy X-ray Microscopy: Present Status and Recent Applications at the ESRF ID22 Beamline

Anatoly Snigirev (snigirev@esrf.fr)

ESRF, BP 220, 38043 Grenoble, France

The advent of third generation synchrotron radiation sources like ESRF, APS and SPring-8 has revived the interest of hard x-ray microscopy. The very low divergence and high coherence of the beams allow efficient focusing down to a submicron spot sizes using Bragg-Fresnel Optics, Fresnel Zone Plates and Compound Refractive Lenses in the energy range from 5 to 60 keV. The availability of the high resolution hard x-ray microscopy techniques is opening up research opportunities for a broad range of disciplines including geoscience applications.

Recently commissioned at the ESRF on ID 22 the Micro- fluorescence, imaging and diffraction (micro-FID) beamline is devoted to the study of samples at the micron and submicron scale. A new flexible setup has been designed to allow the use of the beam after a system of flat mirror and fixed-exit double-crystal monochromator. The accessible energy range (5 - 60 keV) spans K edges to the rare earth's region and L/M edges of all elements. All probes can be used either in the single spot or mapping mode with a sub-micron scanning precision.

The methods of investigation comprise: microspectroscopy (microfluorescence and micro-XANES), microdiffraction (wide- and small-angle scattering) and imaging (phase contrast imaging, microtomography and microtopography). The present status of the hard X-ray microscopy facility allows to use coupled simultaneous diagnostics. Fluorescence-diffraction, fluorescence-XANES, and XANES-tomography were successfully applied for comprehensive characterization of micrometeorites and Uranium fall-out particles. Microfluorescence was used for trace elements mapping of glass and fluid inclusions in minerals. Combination of spectroscopy and diffraction with microtomography provides not only chemical and crystallographic speciation data but also the spatial associations of such information. Time-resolved microimaging, fluorescence tomography and other novel microanalysis are under development and will be available in the near future.

High Energy X-ray Optics for Microanalysis with Synchrotron Radiation

Irina Snigireva (irina@esrf.fr) & Anatoly Snigirev (snigirev@esrf.fr)

ESRF, B.P. 220, 38043 Grenoble, France

X-ray diffraction, fluorescence and imaging are very powerful techniques for the nondestructive studies in experimental mineralogy, petrology and geochemistry. These techniques might benefit much more from increasing the spatial resolution by applying microfocusing optics. Successful commissioning and operation of the third generation of the synchrotron radiation sources such as ESRF give rise to tremendous progress in the development of microfocusing optics. The present status of X-ray optics in high-energy domain will be reviewed with respect to lateral resolution, flux, imaging capability. It has been demonstrated that practically all optical systems have overcome the micrometer barrier and reached a sub-micrometer resolution. Taking into account coherent properties of the X-ray beam, the coherence preservation is precisely, an essential feature, which is required of the focusing optics. This is because the coherent optics like Bragg Fresnel optics (BFO), Fresnel zone plates (FZP), and compound refractive lenses (CRL) shows excellent compatibility with the third generation synchrotron radiation sources. BFO is acting as a focusing monochromator producing a cylindrical wave front and is widely used for high-resolution diffraction studies. This is tuneable focusing device working in the energy range from 6 keV up to 100 keV. The FZP and CRL are used in transmission geometry that considerably simplifies the alignment of both optics and sample, and location an area of interest in the sample. Energy applicability of FZP is limited to 20 keV. Parabolic CRLs, made from polycrystalline aluminium by pressing technique, are genuine focusing devices. They are very robust, easy to align and they can be used in an energy range from 6 keV to 100 keV. Wide range of microbeam applications to study samples from, mineralogy, geology and material science has been performed at the ESRF ID22 beamline. Examples of microprobe experiments including microdiffraction and microspectroscopy will be presented.

Changing in X-ray Ordering in Crystals of Alkali Feldspars from Rhyolites of Subvolcanic Vent (Eldjurtu Massive, Northern Caucasus, Russia)

Roland Sobolev (sobol@geol.msu.ru) & Elena Volkova (elena_cryst@mail.ru)

Geological Faculty, Moscow State University, Moscow 119899, Russia

There were investigated samples of alkali feldspar from subvolcanic Eldjurtu vent by the method of X-ray diffraction. The central (near 1.5 sm) and the ring (not more then 0.5 sm) parts were taken from the crystals with the size 2 sm in length.

Higher degree of ordering is typical for the central part of feldspar crystals (from high microcline up to intermediate orthoclase, the dominate phase is high microcline); lower degree is characteristic to the ring part (from intermediate orthoclase up to high sanidine, the dominate phase-high sanidine).

Established changing in ordering degree is result of crystals growth in different TP conditions. The central part started to crystallized in deep magmatic chamber by high pressure and low temperature decreasing. The ring part was crystallized after rapid rise of acid melt in conditions of low pressure and quick temperature decreasing.