Diffraction based Hanbury Brown and Twiss interferometry at a hard x-ray free-electron laser

Area of Science:

• X-ray science
• Coherent X-ray optics
• Statistical physics

Background:

• X-ray free-electron lasers (XFELs) offer intense, coherent X-ray pulses vital for advanced research.
• Understanding XFEL statistical properties is crucial for accurate experimental interpretation in fields like biology and materials science.

Purpose of the Study:

• To demonstrate Hanbury Brown and Twiss (HBT) interferometry in diffraction mode at an XFEL source for the first time.
• To determine XFEL statistical properties directly from Bragg peaks of colloidal crystals.

Main Methods:

• Implementation of HBT interferometry in a diffraction setup using colloidal crystals.
• Analysis of Bragg peaks to extract statistical properties of XFEL pulses.
• Comparison with traditional HBT interferometry performed in the direct beam.

Main Results:

• Successful demonstration of HBT interferometry in diffraction mode at an XFEL.
• Determination of nearly full (80%) global spatial coherence of XFEL pulses.
• Measurement of an average pulse duration of approximately ten femtoseconds for the monochromatized beam, shorter than electron bunch measurements.

Conclusions:

• HBT interferometry in diffraction mode provides a direct method to characterize XFEL statistical properties.
• The results highlight the high coherence and short pulse duration of the XFEL beam.
• This technique offers valuable insights for optimizing experiments conducted at XFEL facilities.