title: Diffractive-refractive optics: low-aberration Bragg-case focusing by precise parabolic surfaces.
abstract: Based on analytical formulae calculations and ray-tracing simulations a low-aberration focal spot with a high demagnification ratio was predicted for a diffractive-refractive crystal optics device with parabolic surfaces. Two Si(111) crystals with two precise parabolic-shaped grooves have been prepared and arranged in a dispersive position (+,-,-,+) with high asymmetry. Experimental testing of the device at beamline BM05 at the ESRF provided a focal spot size of 38.25 microm at a focal distance of 1.4 m for 7.31 keV. This is the first experiment with a parabolic-shaped groove; all previous experiments were performed with circular grooves which introduced extreme aberration broadening of the focal spot. The calculated and simulated focal size was 10.8 microm at a distance of 1.1 m at 7.31 keV. It is assumed that the difference between the measured and calculated/simulated focal spot size and focal distance is due to insufficient surface quality and to alignment imperfection.
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic v.v.i., CZ-18221 Praha 8, Czech Republic. peter.oberta@psi.ch
authors.forename: P
authors.initials: P
authors.lastname: Oberta
authors.forename: P
authors.initials: P
authors.lastname: Mikulík
authors.forename: M
authors.initials: M
authors.lastname: Kittler
authors.forename: J
authors.initials: J
authors.lastname: Hrdý
authors.forename: L
authors.initials: L
authors.lastname: Peverini
mesh_terms: D016477:Artifacts; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D017356:Synchrotrons / Q000295:instrumentation*; D014965:X-Rays