D2AM, a Beamline with a High-Intensity Point-Focusing Fixed-Exit Monochromator for Multiwavelength Anomalous Diffraction Experiments

Abstract

D2AM is a french CRG beamline installed at the ESRF (European Synchrotron Radiation Facility) in Grenoble, with half of the time dedicated to biological macromolecule crystallography and half to materials science studies (diffraction, wide-angle and small-angle scattering). It is constructed at the front-end BM02 of the ESRF storage ring, using the X-ray beam from a 0.8 T bending magnet. D2AM entered into routine operation at the end of 1994, and is used either for single-wavelength or for multiwavelength anomalous diffraction studies. The beam is monochromated by an Si[111] two-crystal monochromator with a resolution of about 2 x 10(-4). The first crystal is water cooled. The X-ray photon energy covers the range between 6.5 keV (lambda approximately 1.9 A) and 17 keV (lambda approximately 0.7 A), a domain of energy with many K or L absorption edges of heavy atoms of interest for biological macromolecules studies and in materials science. The X-ray beam is focused in the vertical plane by two long curved mirrors and in the horizontal plane by the second crystal of the monochromator which is given an adjustable sagittal curvature. A spot size of 0.3 x 0.1 mm (FWHM) is measured at the sample position. Both mirrors are cut out of a 6"-diameter 1.1 m-long Si single crystal, polished and coated with a 400 A Pt thin film. The rugosity is better than 4 A r.m.s. and the longitudinal slope error is better than 5 x 10(-6) rad r.m.s. The first mirror is water cooled, the second is not. The beam intensity on the sample is about 10(11) photon s(-1) on a 0.3 x 0.3 mm focus area at 100 mA in the storage ring of the ESRF. The harmonic rejection ratio obtained with the two mirrors is better than 10(-5) for lambda/3. The combined optical system, mirror/monochromating-crystals/mirror, used on D2AM constitutes altogether a high-intensity point-focusing fixed-exit monochromator, which has the additional property that the energy resolution is not dependent on the beam divergence in use. Its stability and resolution are perfectly adapted to multiwavelength anomalous diffraction studies. The alignment of the mirrors and the monochromator is fully automated, taking 5 min, with the exception of the adjustment of the sagittal focusing. During multiwavelength diffraction experiments the wavelength is changed by a fast single monochromator rotation. Neither realignment of the mirrors nor readjustment of the beam focusing are necessary. The stability and reproducibility of the selected X-ray photon energy is better than 0.5 eV.

Profile of the induced5dmagnetic moments in Ce/Fe and La/Fe multilayers probed by x-ray magnetic-resonant scattering

“…The experiments have been performed at several photon energies around the L 2 edge of the rare earth and the K edge of Fe by using the diffractometer installed on D2AM, the French CRG beam line at ESRF. 21 The changes in the f Ј values by about 6 electrons at both edges are moderate. Nevertheless, significant variations in the intensities of the diffraction peaks were observed as it is illustrated in Fig.…”

Interfacial structure in (111) Au:Ni multilayers investigated by anomalous x-ray diffraction

“…The mosaicity around the texture axis is about 4°. Experiments were carried out at the beamline D2AM, which is dedicated to anomalous scattering analysis, 24 at the European Synchrotron Radiation Facility ͑ESRF͒ in Grenoble, France. The seven-circle diffractometer available at D2AM was used to put the ͗111͘ texture axis in the diffraction plane ͑with tilt angle ͒.…”

Uranium–molybdenum nuclear fuel plates behaviour under heavy ion irradiation: An X-ray diffraction analysis

“…On the D2AM beamline [21], the photon energy was set to 13 keV. Measurements were performed with a fixed X-ray beam incidence angle (10°) on the sample (to be more sensitive to the 127 I irradiated volume) (Fig.…”