Aberrations of diffractive–refractive optics: Bragg-case sagittal focusing of multiple parabolic elements

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.

Section: Figurementioning

confidence: 57%

“…When the arrangement of the crystals is as shown in Fig. 2, then the focusing equation 2has to be corrected (Hrdý et al, 2005) to…”

Section: Figurementioning

confidence: 99%

Diffractive–refractive optics: low-aberration Bragg-case focusing by precise parabolic surfaces

Oberta

Mikulı́k

Kittler

et al. 2009

“…2). This situation leads to aberrations and thus disagreements between calculation and experiment (Hrdý et al, 2005).…”

Section: Double-crystal Arrangementmentioning

confidence: 99%

X-ray collimation by crystals with precise parabolic holes based on diffractive–refractive optics

Oberta

Mikulik

Kittler

et al. 2011

Two crystals with precise parabolic holes were used to demonstrate sagittal beam collimation by means of a diffractive-refractive double-crystal monochromator. A new approach is introduced and beam collimation is demonstrated. Two Si(333) crystals with an asymmetry angle of α = 15° were prepared and arranged in a dispersive position (+,-,-,+). Based on theoretical calculations, this double-crystal set-up should provide tunable beam collimation within an energy range of 6.3-18.8 keV (Θ(B) = 71-18.4°). An experiment study was performed on BM05 at ESRF. Using 8.97 keV energy, the beam profile at various distances was measured. The experimental results are in good agreement with theoretical predictions. Owing to insufficient harmonic suppression, the collimated (333) beam was overlapped by horizontally diverging (444) and (555) beams.

“…This is the focusing distance created only by the exit surface. The additional effect of the entrance surface may be calculated according to the recurrent formula of Hrdý et al (2005). {Another possibility is simply to replace K in (5) by Lp(cos /cos ( + ) + Lp[cos /cos ( À )].}…”

Section: Figurementioning

confidence: 99%

Diffractive–refractive optics in the Laue case: first experiment

Hrdý¹,

Mocella²,

Oberta³

et al. 2006

The possibility of sagittally focusing synchrotron radiation using an asymmetric Laue crystal with profiled surfaces has been experimentally demonstrated for the first time. The sample was a Si single crystal with two parallel cylindrical holes of diameter 8 mm. The axes of the holes formed an angle of 7.95 degrees with the (111) diffracting planes and were arranged vertically with respect to the diffracting planes. 15.35 keV synchrotron radiation was diffracted in the space between the holes. The minimum thickness of this Laue crystal was 0.5 mm. The diffracted beam formed an angle of 0.55 degrees with the exit surface. The experiment was performed at beamline BM05 at the ESRF. The length of the beamline was not sufficiently long to detect the focus, but the experiment clearly showed that the diffracted beam was sagittally convergent.