Increased spatial coherence length from an asymmetric crystal reflection at grazing exit

Area of Science:

• * Synchrotron radiation science
• * Coherent X-ray imaging
• * Optics and beam manipulation

Background:

• * Coherent X-ray imaging relies on sufficient spatial coherence length (SCL) and field of view.
• * Standard double-crystal monochromators (DCMs) at synchrotrons often limit the achievable SCL.
• * Increasing SCL is vital for advancing coherent diffraction imaging techniques.

Purpose of the Study:

• * To investigate methods for enhancing the spatial coherence length (SCL) of X-ray beams from a DCM.
• * To evaluate an experimental arrangement using asymmetric crystal diffraction for SCL improvement.
• * To compare the effectiveness of this method with other SCL enhancement strategies.

Main Methods:

• * Utilized Talbot interferometry to measure SCL.
• * Employed ray-tracing simulations for a four-reflection optical setup.
• * Investigated an asymmetric crystal reflection at grazing exit following a DCM.

Main Results:

• * Achieved a 76% gain in SCL compared to the beam exiting the DCM.
• * Observed a 20-fold reduction in flux density, deemed acceptable for synchrotrons.
• * Simulations showed significantly reduced SCL when asymmetric crystals are used at grazing incidence.

Conclusions:

• * An asymmetric crystal reflection at grazing exit effectively enhances SCL for coherent X-ray imaging.
• * The trade-off of reduced flux density is manageable at synchrotron facilities.
• * This method offers a viable alternative to beam focusing or extended vacuum propagation for SCL improvement.