M Lingham | PubMed Health

PubMed1998

X-ray magnetic reflectometry using circularly polarized radiation.

Magnetic reflectometry experiments have been performed in the X-ray range at the L(2,3) edges of rhodium. What makes these experiments original is the insertion of a very compact double-bounce reflectometer upstream of the monochromator. This configuration makes full use of the high polarization rate of the helical undulator source. This advantage is reflected in the high quality of the data obtained after only a few accumulations. It is also shown that, by properly selecting the angle of incidence, one may obtain experimental differential X-ray reflectivity spectra dominated either by the dispersion or the absorption terms.

Journal Article↗

PubMed1998

Focusing Optics for High-Energy X-ray Diffraction.

Novel focusing optical devices have been developed for synchrotron radiation in the energy range 40-100 keV. Firstly, a narrow-band-pass focusing energy-tuneable fixed-exit monochromator was constructed by combining meridionally bent Laue and Bragg crystals. Dispersion compensation was applied to retain the high momentum resolution despite the beam divergence caused by the focusing. Next, microfocusing was achieved by a bent multilayer arranged behind the crystal monochromator and alternatively by a bent Laue crystal. A 1.2 micro m-high line focus was obtained at 90 keV. The properties of the different set-ups are described and potential applications are discussed. First experiments were performed, investigating with high spatial resolution the residual strain gradients in layered polycrystalline materials. The results underline that focused high-energy synchrotron radiation can provide unique information on the mesoscopic scale to the materials scientist, complementary to existing techniques based on conventional X-ray sources, neutron scattering or electron microscopy.

Journal Article↗