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| TUBAU03 |
Cross-Correlation between a VUV-FEL and an Optical Laser
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291 |
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- Th. Maltezopoulos, U. Fruehling, E. Plönjes
DESY, Hamburg
- C. Cunovic, N. Mueller
Universität Bielefeld, Bielefeld
- M. Drescher, R. Kalms, M. Krikunova, M. Wieland
Uni HH, Hamburg
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At the Free Electron Laser in Hamburg (FLASH) a synchronized 800 nm optical laser is available for time-resolved VUV/vis pump-probe experiments. We crossed both femtosecond pulses in a Kr gas target and imaged the created photoelectrons with an energy-dispersive electron spectrometer. In the region where both pulses overlap in space and time, the photoelectrons are energetically shifted and form spectral sidebands. The imaging electron spectrometer projects the spectral- into an intensity modulation, thus, mapping time into space. This way, the technique delivers information about the relative timing between VUV- and visible pulse and is non invasive for both pulses. While observation of the cross-correlation signal currently requires data-averaging, with proper focussing single shot capability shall be reached, thereby enabling pulse-to-pulse jitter measurements.
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| FRAAU03 |
Wave-Front Observations at FLASH
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794 |
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- M. Kuhlmann, E. Plönjes, K. I. Tiedtke, S. Toleikis
DESY, Hamburg
- P. Mercere
SOLEIL, Gif-sur-Yvette
- P. Zeitoun
LOA, Palaiseau
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During the first user operation of the Free-Electron Laser in Hamburg (FLASH) wavefront measurements have been recorded in the vacuum-ultraviolet region using a Hartmann sensor (by Imagine Optic). The Hartmann principle is based on a pinhole array, which divides the incoming beam into a large number of sub-rays monitored in intensity and position of individual spots. The identification of the local slope of the incident wavefront makes the aberrations from a perfect spherical wavefront visible. Ray tracing in upstream direction accesses the beam focal point in size and position. The intense and coherent vacuum-ultraviolet FEL beam leads to unique requirements for the wavefront sensor setup. We report an optimized setup to observe the metrology of flat and curved mirrors at FLASH beamlines. The effects of solid and gaseous filters are selectively described in the wavelength regime of 10nm to 32nm. The use of wavefront measurements to provide reliable machine parameter is discussed. The wavefront sensor proved to be a valuable tool to observe the FEL beam quality and the performance of optical elements, filters and diagnostic tools.
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Slides
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Talk
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