Plasma emission spectroscopy of solids irradiated by intense XUV pulses from a free electron laser

Abstract

a b s t r a c tThe FLASH XUV-free electron laser has been used to irradiate solid samples at intensities of the order 10 16 W cm À2 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 10 21 -10 22 cm À3 . These results are consistent with the saturation of absorption through bleaching of the L-edge by intense photo-absorption reported in an earlier publication.

XUV spectroscopic characterization of warm dense aluminum plasmas generated by the free-electron-laser FLASH

“…Over a period of more than four years, the authors have conducted a series of experimental, theoretical, and computational investigations (Zastrau et al, 2008;Vinko et al, 2009Vinko et al, , 2010Nagler et al, 2009;Cihelka et al, 2009;Toleikis et al, 2010;Dzelzainis et al, 2010;Galtier et al, 2011;Medvedev et al, 2011) at the extreme ultraviolet (XUV) free-electron laser in Hamburg (FLASH (Tiedtke et al, 2009)) aiming at the generation and characterization of photo-induced Al plasma. Our knowledge about optical parameters and the primary response of the sample under irradiation with FLASH was significantly increased.…”

“…In experiments at BL3 (Dzelzainis et al, 2010), we employed a single-optics grating spectrometer. This setup is based on a Hitachi 1200 lines/mm variable line spacing grating (Nakano et al, 1984) and creates a flat spectral focus plane on an Andor DX420-BN CCD camera positioned on a vacuum flange with the chip in vacuum.…”

“…A thin Al foil filter was used to establish the spectral resolution. We achieved a resolution of 0.1 nm, determined from the steepness of the Al L absorption edge (Dzelzainis et al, 2010). As target, an Al foil target 10 μm thick was moved across the FLASH focus continuously, to expose a fresh surface to each shot.…”

“…Statistical analysis of the data in this range yielded 40.5 eV for the free-electron-temperature with a root-mean-square (RMS) error of ± 5.5 eV. Dzelzainis et al (2010) also investigated the continuum emission from Al and higher Z targets such as Fe and Co at peak intensities of several 10 16 W/cm 2 at BL3. In all cases, both teams got similar temperatures from 30 to 40 eV, which is significantly lower than the expected temperatures for linear absorption.…”

Technical Applications of the Physics of High Energy Densities

“…7.49) [42,64,66,77,126,137,152,173,174,179,210,236,238,248]. This will enable, in particular, studies of three-dimensional biological structures as well as determination of the location and role of its specific constituent structural elements, which is of great importance in developing new-generation medicines and polymers, as well as in constructing complex spatial molecular structures.…”