Professor Justin Wark

Abstract:

The FLASH XUV-free electron laser has been used to irradiate solid samples at intensities of the order 1016 W cm-2 at a wavelength of 13.5 nm. The subsequent time integrated XUV emission was observed with a grating spectrometer. The electron temperature inferred from plasma line ratios was in the range 5-8 eV with electron density in the range 1021-1022 cm-3. These results are consistent with the saturation of absorption through bleaching of the L-edge by intense photo-absorption reported in an earlier publication. © 2009 Elsevier B.V. All rights reserved.

Abstract:

The analysis of the radiative properties of plasmas created by XUV and X-ray free electron laser radiations provides a tremendous challenge to researchers to investigate matter under extreme conditions. In the present work we report about the theoretical analysis of the radiation emission of Al heated by the interaction of 10 fs focused (1 μm) free electron laser radiation at 13.5 nm at intensities of about 1016 W/cm2. The data show strong resonance line emission 3l -2l′ from Ne-like Al but also numerous intense broad emission structures in the spectral range from 10-30 nm. Atomic structure analysis indicate that these emission structures might originate from multiple excited states with L-holes. By means of a genetic algorithm we analyze possible excitation channels driven directly by the FLASH free electron laser as well as by heated plasma electrons.