RESUMEN
Grazing incidence mirrors are used on most X-ray synchrotron beamlines to focus, collimate or suppress harmonics. Increasingly beamline users are demanding variable beam shapes and sizes at the sample position. We have now developed a new concept to rapidly vary the beam size and shape of a focused X-ray beam. The surface of an elliptically figured mirror is divided into a number of laterally separated lanes, each of which is given an additional longitudinal height profile calculated to shape the X-ray beam to a top-hat profile in the focal plane. We have now fabricated two prototype mirrors and present the results of metrology tests and measurements made with one of the mirrors focusing the X-rays on a synchrotron beamline. We envisage that such mirrors could be widely applied to rapid beam-size switching on many synchrotron beamlines.
RESUMEN
This paper discusses the possibility of using Compton scattering--an inelastic X-ray scattering process that yields a projection of the electron momentum density--to probe magnetoelectrical properties. It is shown that an antisymmetric component of the momentum density is a unique fingerprint of such time- and parity-odd physics. It is argued that polar ferromagnets are ideal candidates to demonstrate this phenomenon and the first experimental results are shown, on a single-domain crystal of GaFeO3. The measured antisymmetric Compton profile is very small (≃ 10(-5) of the symmetric part) and of the same order of magnitude as the statistical errors. Relativistic first-principles simulations of the antisymmetric Compton profile are presented and it is shown that, while the effect is indeed predicted by theory, and scales with the size of the valence spin-orbit interaction, its magnitude is significantly overestimated. The paper outlines some important constraints on the properties of the antisymmetric Compton profile arising from the underlying crystallographic symmetry of the sample.
RESUMEN
Multilayers are becoming an increasingly important tool in X-ray optics. The essential parameters to design a pair of laterally graded multilayer mirrors arranged in a Montel-type configuration for use as an X-ray collimating device are provided. The results of X-ray reflectometry tests carried out on the optics in addition to metrology characterization are also shown. Finally, using experimental data and combined with X-ray tracing simulations it is demonstrated that the mirror meets all stringent specifications as required for a novel ultra-high-resolution inelastic X-ray scattering spectrometer at the Advanced Photon Source.
RESUMEN
The beamline, which is situated on a bending magnet at ESRF, comprises a unique combination of instrumentation for high-resolution and magnetic single-crystal diffraction. White-beam operation is possible, as well as focused and unfocused monochromatic modes. In addition to an eleven-axis Huber diffractometer, which facilitates simple operation in both vertical and horizontal scattering geometries, there is an in-vacuum polarization analyser and slit system, mirrors for harmonic rejection, sub 4.2 K and 1 Tesla magnetic field sample environment, plus a diamond phase plate for polarization conditioning. The instrumentation developed specifically for this beamline is described, and its use illustrated by recent scientific results.
RESUMEN
The ratio of the magnetic to the charge form factors of nickel has been determined by white-beam X-ray diffraction. The measurements were made on the new UK magnetic scattering beamline (XMaS) on a dipole source at the ESRF. The data comprise the three (h,h,0) reflections (4,4,0), (6,6,0) and (8,8,0) and the seven high-order (h,0,0) reflections (6,0,0) to (18,0,0), which doubles the range of wavevectors compared to previous studies. The data have been analysed using Hartree-Fock free-ion wave functions and core electron polarization effects were included. The results support the interpretation of neutron data obtained at lower momentum transfer for the e(g) and t(2g) orbital occupancies. The polarization of the dipole source is deduced to vary from 99.88 to 99.83% between 5 and 15 keV, respectively. This high value makes it an extremely suitable source for studies of ferromagnetism.
RESUMEN
The magnetic form factor of nickel has been measured, as a fraction of the charge form factor for {h00} and {hhh} reflections up to (10 00) and (666), by an x-ray energy dispersive white beam technique that uses elliptically polarized synchrotron radiation and single crystal samples. At low sin(θ)/λ the results are in good agreement with theory and with the values determined from neutron studies. The measurements extend beyond the current range of neutron data and indicate that significant magnetic diffraction effects are observable at sin(θ)/λ > 1.5 Å-1 if photons with energies above 26 keV can be used.