Center of mass grain maps in 3D
J.P. Wright, G.B.M. Vaughan, S. Schmidt, Henning Friis Poulsen, Cortney Gundlach · Acta Crystallographica Section A Foundations of Crystallography · 2008
X-ray focusing technique is essential for probing microscopic samples at high pressures.Compound refractive lens (CRL) is one of the most versatile devices that are capable of focusing and collimating x-rays in the high-energy range of 20-60 keV [1, 2].The CRL offers many advantages: good efficiency for focusing, compactness, robustness, and easy alignment (in-line focusing element).At high-pressure x-ray diffraction beamline BL10XU of SPring-8, the x-ray focusing optics consisting two different types of CRL devices have been installed in tandem.The first CRL (16 m focal distance) made from glassy carbon (GC), which is situated at a distance of 42 m from the source, has been used incidentally to collimate the x-ray beam.The aperture of this CRL is about 1 mm, whose size matches the beam size of the undulator.Because of difficulty in focusing the x-ray beam size down to 10µm through the first CRL, a second focusing CRL device was placed at 0.5 m upstream to the sample.The second CRL is sets of planar crosslenses with a quasi-parabolic profile for focusing in two directions, and were fabricated from SU-8 polymer by deep x-ray lithography at the ANKA in Germany [3].The placement of the SU-8 CRL after the GC-CRL produces an x-ray beam with a spot size of less than 7 µm at 30 keV.The photon flux density at the focal point is approximately 10 15 photons/sec/mm 2 .This x-ray optics allow us to collect highquality x-ray diffraction data on materials subjected to extreme pressures of up to 400 GPa, which exceeds the condition found at the Earth's center.[1]