UVX 2008 (2009) 113-118
DOI: 10.1051/uvx/2009018

Characterization of the FLASH XUV-FEL pulses by two-color photoionization experiments

M. Meyer¹, D. Cubaynes¹, D. Glijer¹, S. Düsterer², W.B. Li², A. Azima², H. Redlin², J. Feldhaus², J. Dardis³, P. Hayden³, P. Hough³, V. Richardson³, E.T. Kennedy³, J.T. Costello³, R. Taïeb⁴, A. Maquet⁴, E.V. Gryzlova⁵, S.I. Strakhova⁵ and A.N. Grum-Grzhimailo<sup>1, 5

1</sup>  LIXAM, UMR 8624, CNRS - Université Paris Sud, Bâtiment 350, 91405 Orsay Cedex, France
²  HASYLAB at DESY, Notkestr. 85, 22607 Hamburg, Germany
³  National Center for Plasma Science and Technology and School of Physical Sciences, Dublin City University, Dublin 9, Ireland
⁴  UPMC, Université Paris 06, CNRS, UMR 7614, LCPMR, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
⁵  Institute of Nuclear Physics, Moscow State University, Moscow 119991, Russia

Published online: 7 July 2009

Abstract
The current key performance indicators of the pump-probe facility at the Free Electron Laser in Hamburg (FLASH) are described. The temporal and spatial characteristics of both the extreme ultra-violet (XUV) Free Electron Laser and the temporally synchronized optical femtosecond Ti:Sapphire laser are determined by measuring two-color above threshold ionization in rare gases. Characteristic sidebands appear in the photoelectron spectrum under the combined action of both radiation fields providing a very sensitive probe for the spatial and temporal overlap of both pulses. The high spatial acceptance of a magnetic bottle electron spectrometer enabled us to obtain single-shot photoelectron spectra and to correct for the inherent time jitter between both light sources, which reduces the temporal resolution when recording spectra in average mode. As an illustration of the first application, % of the pump-probe set-up, experimental results on polarization control in the two-photon two-color ionization of atomic He are presented.

© EDP Sciences 2009