Construction of a precision diffractometer for nuclear Bragg scattering at the Photon Factory

Abstract

A versatile precision diffractometer for nuclear Bragg scattering was designed and constructed at the Photon Factory. Standardized component goniometers can be arranged to address various requirements of incident beam conditioning for nuclear Bragg scattering, including a high-energy resolution monochromator with wide angular acceptance as well as a circularly polarized incident beam.

An X-ray scattering beamline for studying dynamics

“…Other monochromator designs (e.g. [25]) were considered, and are used for IXS at APS [9,10]. However, the difficulties associated with accommodating the finite (though small) angular divergence of the X-ray beam reduce the throughput of these designs as compared to a single back reflecting crystal: relative losses of about a factor of two were expected at low (ϳ15 keV) energies and a factor of 4 or more at higher energies (above 20 keV).…”

“…The first hutch will be primarily for high-resolution optics (e.g. [25,30,31]) while the second hutch will be for samples. This separation is to allow access to the sample without any disturbance to the high-resolution optics.…”

Experimental facilities

“…Sapphire (Al 2 O 3 ) significantly increases the tuning range and the energy-range, but so far, sapphire crystals of the required quality and size are not available. Nested monochromators can reach an energyresolution of 5-10 meV with a tunability of a few eV, but only at a few energies close to the backscattering energies of specific reflections of Si [15][16][17]. A third option was recently proposed by Shvyd'ko: Three crystals collimate the beam, monochromatize it, and focus it again.…”

“…Several back scattering analyzer systems with energy-resolution of 100 meV (1 meV) using spherically bent analyzers with radii of curvature of 3 m (7-11 m) have demonstrated their high efficiency over the past decade [11,[16][17][18][19]. The future challenge will be to build a spectrometer that will be capable of determining the energy of scattered photons with high energy resolution at angles smaller than backscattering, e.g., the fluorescence lines of 3d and 4f elements, which are not close to backscattering energies of either Si or Ge reflections.…”

Wavelength-dispersive double flat-crystal analyzer for inelastic X-ray scattering

“…We suggest the use of a double¯at-crystal arrangement, which has been discussed elsewhere (Beaumont & Hart, 1974;Nakayama et al, 1973) and was recently used for high-resolution monochromatization (Ishikawa et al, 1992;Toellner, 1996Toellner, , 2000Chumakov et al, 1996;Toellner et al, 1997). These monochromators consist of two perfect crystals and the usually high-index Bragg re¯ections are in dispersive arrangement.…”