Measuring the criticality of the `magic condition' for a beam-expanding monochromator

It has been established that for cylindrically bent crystals the optimal beam characteristics occur when the geometric and single-ray foci are matched. In the beam-expanding monochromator developed for the BioMedical Imaging and Therapy beamlines at the Canadian Light Source, it was unclear how critical this `magic condition' was for preserving the transverse coherence of the beam. A study was conducted to determine whether misalignments away from the ideal conditions would severely affect the transverse coherence of the beam, thereby limiting phase-based imaging techniques. The results were that the magic condition has enough flexibility to accommodate deviations of about ± 1 ° or   ± 5   keV.

Source: Journal of Synchrotron Radiation - October 5, 2016 Category: Physics Authors: Martinson, M. Chapman, D. Tags: magic condition bent Laue double-crystal monochromator geometric and polychromatic focus short communications Source Type: research