Beam parameters of the free-electron laser FLASH @13.5 nm in two different operation modes were determined from beam profile measurements and subsequent reconstruction of the Wigner distribution function behind the ellipsoidal focusing mirror at beamline BL2. 40 two-dimensional single pulse intensity distributions were recorded at each of 65 axial positions around the waist of the FEL beam with a magnifying EUV sensitized CCD camera. From these beam profile data the Wigner distribution function based on different levels of averaging could be reconstructed by an inverse Radon transform. For separable beams this yields the complete Wigner distribution, and for beams with zero twist the information is still sufficient for wavefront determination and beam propagation through stigmatic systems. The obtained results are compared to wavefront reconstructions based on the transport of intensity equation. A future setup for Wigner distribution measurements of general beams is discussed.

Date Published: 3 May 2013
PDF: 11 pages
Proc. SPIE 8778, Advances in X-ray Free-Electron Lasers II: Instrumentation, 877810 (3 May 2013); doi: 10.1117/12.2016975

Published in SPIE Proceedings Vol. 8778:
Advances in X-ray Free-Electron Lasers II: Instrumentation
Thomas Tschentscher; Kai Tiedtke, Editor(s)