title: Measuring the criticality of the `magic condition' for a beam-expanding monochromator.
abstract: 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.
authors: Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Rm 163, Saskatoon, Saskatchewan, Canada S7N 5E2.
authors: Mercedes
authors: M
authors: Martinson
authors: Canadian Light Source, 44 Innovation Boulevard, Saskatoon, Saskatchewan, Canada S7N 2V3.
authors: Dean
authors: D
authors: Chapman
keywords: bent Laue double-crystal monochromator; geometric and polychromatic focus; magic condition