Versatile collimating crystal stage for Bonse-Hart USAXS instrument.

Conference · Mon Jan 01 04:00:00 EST 2007

DOI:https://doi.org/10.1063/1.2436427· OSTI ID:970768

Ilavsky, J; Shu, D; Jemian, P R; Long, G G

An advanced ultra-small-angle X-ray scattering (USAXS) instrument, using the Bonse-Hart design and installed at APS, is a robust and reliable instrument, providing a scattering vector (q) range of nearly 4 decades (0.00015 to 1 {angstrom}{sup -1}), an intensity dynamic range of up to 9 decades, standard-less absolute intensity calibration, and USAXS imaging capabilities. This type of instrument typically uses channel-cut crystals in both the collimating (before sample) and analyzing (after sample) stages. The optical surfaces of these crystals are finished by etching processes, which leave an orange-peel surface texture, which would compromise the USAXS imaging quality. Therefore optics with highly polished surfaces using separated crystals in both collimating and analyzing stages were developed. A novel design of the optics and mechanical stage uses a fixed gap between the two separated collimating crystals in which a triangular section of the first crystal is removed, allowing for a variable number (1, 2, 4, 6, or 8) of crystal reflections for X-ray energies between 7 and 19 keV. The number of reflections is selected by lateral translation of the collimating crystal pair. Rotational alignment of the second crystal in the pair by an artificial channel-cut crystal mechanism, implemented with a novel high-stiffness weak link actuated by both a picomotor and a piezo-electric transducer, provides the capability to align or adjust an assembly of crystals to achieve the same performance as a single channel-cut crystal with integral weak link. The arrangement of both crystals is held on a removable base that can be remounted with precision within the Si(111) rocking curve on a three-point kinematic mount. Additional tilt adjustments are also provided for initial alignment. This monochromator has proven to be highly robust with respect to motions and vibrations, as well as flexible with respect to selection of number of reflections, and its performance directly resulted in the highly reliable performance of the whole USAXS instrument.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: SC
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 970768
• Report Number(s): ANL/XFD/CP-118731
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

43 PARTICLE ACCELERATORS
ACCURACY
ALIGNMENT
CALIBRATION
DESIGN
ETCHING
MONOCHROMATORS
NEUTRON DIFFRACTION
OPTICS
PERFORMANCE
SCATTERING
SYNCHROTRON RADIATION
TEXTURE
VECTORS