Dresden 2009 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 31: Application of Thin Films II
DS 31.2: Vortrag
Donnerstag, 26. März 2009, 16:30–16:45, GER 37
Effect of FEL induced ionization on X-ray reflectivity of multilayers — •Dmitriy Ksenzov, Souren Grigorian, and Ullrich Pietsch — University of Siegen, Siegen, Germany
The VUV-FEL in Hamburg (FLASH) emits short-pulse radiation with wavelengths from 6 to 30 nm and a pulse length of 10-50 fs. The FLASH wavelength allows x-ray diffraction experiments at periodical multilayer’s structures acting as 1D crystal. The probe of depth selective interaction of the high-intense x-ray short pulse with these objects can be used to obtain information about possible electronic excitation and various recombination processes inside multilayers. As known from recent experiments at FLASH, the later ones are most likely using highly intense FEL radiation.
The ML reflectivity is analyzed for case of that the optical parameters are changing as function of the depth of the penetrating incident pulse into the multilayer. The response is studied for the model system La/B4C using two experimental conditions both at fixed incidence angle: 1) the energy of the incident pulses, E, coincides with the energy of the 1st order multilayer Bragg peak, EB, of the reflection curve, and 2) the energy of incident pulse differs by a small dE from EB. The ML response to a given sub-pulse differs for both conditions. However, there is a clear fingerprint of ionization for both conditions for the case that E is close to the K-absorption edge of B-atoms. Our results support respective efforts to measure the optical parameters of solids under high-intense FEL radiation.