title: Heat bump on a monochromator crystal measured with X-ray grating interferometry.
abstract: Deformation of the first crystal of an X-ray monochromator under the heat load of a high-power beam, commonly referred to as `heat bump', is a challenge frequently faced at synchrotron beamlines. Here, quantitative measurements of the deformations of an externally water-cooled silicon (111) double-crystal monochromator tuned to a photon energy of 17.6 keV are reported. These measurements were made using two-dimensional hard X-ray grating interferometry, a technique that enables in situ at-wavelength wavefront investigations with high angular sensitivity. The observed crystal deformations were of the order of 100 nm in the meridional and 5 nm in the sagittal direction, which lead to wavefront slope errors of up to 4 µrad in the meridional and a few hundred nanoradians in the sagittal direction.
authors: Paul Scherrer Institut, 5232 Villigen PSI, Switzerland. simon.rutishauser@psi.ch
authors: Simon
authors: S
authors: Rutishauser
authors: Alexander
authors: A
authors: Rack
authors: Timm
authors: T
authors: Weitkamp
authors: Yves
authors: Y
authors: Kayser
authors: Christian
authors: C
authors: David
authors: Albert T
authors: AT
authors: Macrander
keywords: double-crystal monochromator; grating interferometry; heat bump; wavefront characterization