Hamburg 2009 – scientific programme
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A: Fachverband Atomphysik
A 2: Interaction with VUV and X-Ray Light I
A 2.5: Talk
Monday, March 2, 2009, 12:15–12:30, VMP 6 HS-E
Two photon double ionization of He+: autocorrelation of soft x-ray FEL pulses — •Björn Siemer1, Sebastian Roling1, Rolf Mitzner1,2, Tino Noll2, Andrei Sorokin3, Mathias Richter3, Kai Tiedtke4, Wolfgang Eberhardt2, and Helmut Zacharias1 — 1Physikalisches Institut, Westfälische Wilhelms-Universität, 48149 Münster — 2Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Glienicker Straße 100, 14109 Berlin — 3PTB, Abbe-Str. 2-12, 10578 Berlin — 4DESY, Notkestr. 85, 22603 Hamburg
In order to perform jitter-free X-ray pump and probe experiments at the Free Electron Laser in Hamburg (FLASH) as well as to characterize the temporal structure of its high power pulses a novel beam splitter and delay unit (autocorrelator) has been designed and constructed. Based on geometrical beam splitting by a mirror edge the apparatus covers the XUV energy range up to photon energies of 200 eV providing a total delay of about 20 picoseconds with sub-femtosecond resolution. As a first test the pulse length of the FEL pulses has been measured at 24 nm. While the nonlinear autocorrelation in the UV and visible regions is a well established method to determine the duration of laser pulse there is a lack of efficient nonlinear detection processes in the soft X-ray regime. In this first experiments the pulse length of the FEL pulses provided at 24 nm are measured by double ionization of He, yielding a duration of (30 ± 5) fs.