P. Skopintsev1,2,3, A. Singer1, J. Bach4, L. Müller1, B. Beyersdorff2, S. Schleitzer1, O. Gorobtsov1, A. Shabalin1, R.P. Kurta1, D. Dzhigaev1,5, O.M. Yefanov1, L. Glaser1, Sakdinawat6, G. Grübel1,7, R. Frömter4, H.P. Oepen4, J. Viefhaus1, I.A. Vartanyants1,5

Characterization of Spatial Coherence of Synchrotron Radiation with Non-Redundant Arrays of Slits.

Double pinholes (DP) diffraction and coherence

Light beam passing two slits forms a spot with interference pattern. Contrast depends on beam spatial coherence, which can be measured as satellite peak heights in Fourier space of the detector image.

3. Multiple slits diffraction (NRA)

Peak heights:

Each satellite peak corresponds to certain distance at which spatial coherence can be found [3]

1.

Complex degree of coherence (CDC)

CDC can be taken as a measure of spatial coherence if time effects on contrast are low [2], i.e.

Experiment : P04 beamline layout, PETRA III at DESY

Transverse coherence measured with DP

Transverse coherence measured with NRA‘s

[1] P.Skopintsev et al., J. Synchrotron Rad. (2014), 21

[2] J.W. Goodman, Statistical optics

[3] Y. Mejia and A. I. Gonzalez, Opt. Commun. (2007), 273, 428

Contact e-mail: peter.skopintsev@gmail.com

> Results with NRAs and double pinholes are identical.

> NRA method works better with large beams.

> NRA approach allows to measure transverse coherence at several distances simultaneously.

> It might be extremely useful for unstable radiation sources such as free electron lasers.

Transverse coherence for different photon energies

403 eV400 eV396.5 eV

Conclusions & Outlook

References

1. Monochromator exit slits adjust photon energy.

2. Coherence length different for different energies.3. Highest for blue-shifted beam.

Fourier space

Diffraction pattern

Results

Six slits

15 distances

Two pinhol

es

1 distance

400 eV

800 eV (low)

- Six slits NRA

- Double pinholes

Fourier space

Diffraction pattern

1. Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany 2. National Research Center ‘Kurchatov Institute’, Kurchatov Square 1, 123182 Moscow, Russia 3. Moscow Institute of Physics and Technology (State University), Dolgoprudny, 141700, Russia 4. Universität Hamburg, Institut für Angewandte Physik, 20355 Hamburg, Germany 5. National Research Nuclear University, ‘MEPhI’, 115409 Moscow, Russia 6. SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA 7. The Hamburg Center for Ultrafast Imaging, 22761 Hamburg, Germany

Theory

2.Diffraction pattern

Fourier space

0.

Fully coherentPart. coherentIncoherent

Introduction

We present a method to characterize spatial cohe-rence of soft X-ray radiation from a single diffraction pattern. The technique is based on scattering from non-redundant arrays (NRA) of slits and records the degree spatial coherence at several separations from one to 15 µm. Using NRAs we mea-sured vertical spatial cohe-rence of P04 beamline of PETRA III synchrotron for different beam parameters [1]. To verify the results obtained with NRAs additional Young’s double pinholes experiments were conducted and show good agreement.

Beam FWHM = 11 ± 1 µm

Beam FWHM = 42 ± 2 µm