Asymmetric-cut variable-incident-angle monochromator

Journal Article · Thu Mar 15 04:00:00 EDT 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3685614· OSTI ID:22072265

Smither, R K; Fernandez, P B; Mills, D M ^[1]; Graber, T J ^[2]

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1. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2. Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637 (United States)

A novel asymmetric-cut variable-incident-angle monochromator was constructed and tested in 1997 at the Advanced Photon Source of Argonne National Laboratory. The monochromator was originally designed as a high heat load monochromator capable of handling 5-10 kW beams from a wiggler source. This was accomplished by spreading the x-ray beam out on the surface an asymmetric-cut crystal and by using liquid metal cooling of the first crystal. The monochromator turned out to be a highly versatile monochromator that could perform many different types of experiments. The monochromator consisted of two 18 deg. asymmetrically cut Si crystals that could be rotated about 3 independent axes. The first stage ({Phi}) rotates the crystal around an axis perpendicular to the diffraction plane. This rotation changes the angle of the incident beam with the surface of the crystal without changing the Bragg angle. The second rotation ({Psi}) is perpendicular to the first and is used to control the shape of the beam footprint on the crystal. The third rotation ({Theta}) controls the Bragg angle. Besides the high heat load application, the use of asymmetrically cut crystals allows one to increase or decrease the acceptance angle for crystal diffraction of a monochromatic x-ray beam and allows one to increase or decrease the wavelength bandwidth of the diffraction of a continuum source like a bending-magnet beam or a normal x-ray-tube source. When the monochromator is used in the doubly expanding mode, it is possible to expand the vertical size of the double-diffracted beam by a factor of 10-15. When this was combined with a bending magnet source, it was possible to generate an 8 keV area beam, 16 mm wide by 26 mm high with a uniform intensity and parallel to 1.2 arc sec that could be applied in imaging experiments.

• OSTI ID: 22072265
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 3 Vol. 83; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ADVANCED PHOTON SOURCE
BEAM PROFILES
BRAGG REFLECTION
CRYSTALS
DIFFRACTION
HEATING LOAD
KEV RANGE
MONOCHROMATIC RADIATION
MONOCHROMATORS
PHOTON BEAMS
ROTATION
SILICON
WAVELENGTHS
WIGGLER MAGNETS
X RADIATION
X-RAY TUBES