Diffractive-refractive optics: low-aberration Bragg-case focusing by precise parabolic surfaces.
P Oberta1, P Mikulík, M Kittler
1Institute of Physics, Academy of Sciences of the Czech Republic v.v.i., CZ-18221 Praha 8, Czech Republic. peter.oberta@psi.ch
Journal of Synchrotron Radiation
|December 24, 2009
Summary
Researchers developed a novel diffractive-refractive crystal optics device using parabolic grooves. This new design significantly reduces aberrations, achieving a smaller focal spot compared to previous circular groove designs.
Area of Science:
- Optics
- Crystallography
- Materials Science
Background:
- Diffractive-refractive optics are crucial for focusing radiation.
- Previous designs using circular grooves suffered from significant aberration broadening.
- Parabolic surfaces offer potential for improved optical performance.
Purpose of the Study:
- To predict and experimentally validate a low-aberration focal spot using a diffractive-refractive crystal optics device with parabolic surfaces.
- To investigate the performance of parabolic-shaped grooves in X-ray optics.
- To compare experimental results with analytical calculations and ray-tracing simulations.
Main Methods:
- Analytical formulae calculations and ray-tracing simulations were employed to predict optical performance.
- Two Si(111) crystals with precisely shaped parabolic grooves were fabricated.
- The device was tested at beamline BM05 at the European Synchrotron Radiation Facility (ESRF) using a dispersive (+,-,-,+) arrangement with high asymmetry.
Main Results:
- A low-aberration focal spot with high demagnification was predicted.
- Experimental testing yielded a focal spot size of 38.25 microm at 1.4 m for 7.31 keV.
- Calculated and simulated focal size was 10.8 microm at 1.1 m, indicating a discrepancy attributed to surface quality and alignment.
Conclusions:
- The use of parabolic-shaped grooves in diffractive-refractive crystal optics shows promise for reducing aberrations.
- Experimental results, while showing a larger focal spot than predicted, demonstrate the potential of this novel design.
- Further improvements in surface quality and alignment are necessary to fully realize the predicted performance of parabolic groove optics.
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