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Photo-ionized neon plasmas induced by radiation pulses of a laser-plasma EUV source and a free electron laser FLASH

Published online by Cambridge University Press:  27 March 2013

A. Bartnik*
Affiliation:
Institute of Optoelectronics, Military University of Technology, Warsaw, Poland
R. Fedosejevs
Affiliation:
University of Alberta, Edmonton, Canada
P. Wachulak
Affiliation:
Institute of Optoelectronics, Military University of Technology, Warsaw, Poland
H. Fiedorowicz
Affiliation:
Institute of Optoelectronics, Military University of Technology, Warsaw, Poland
C. Serbanescu
Affiliation:
University of Alberta, Edmonton, Canada
E.G. Saiz
Affiliation:
Centre for Plasma Physics, Queen's University Belfast, United Kingdom
D. Riley
Affiliation:
Centre for Plasma Physics, Queen's University Belfast, United Kingdom
S. Toleikis
Affiliation:
Deutsches Elektronen-Synchrotron, Hamburg, Germany
D. Neely
Affiliation:
Central Laser Facility, Rutherford Appleton Laboratory, Oxon, United Kingdom
*
Address correspondence and reprint requests to: A. Bartnik, Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland. E-mail: [email protected]

Abstract

In this work, a laser-produced plasma extreme ultraviolet source and a free electron laser were used to create Ne photo-ionized plasmas. In both cases, a radiation beam was focused onto a gas stream injected into a vacuum chamber synchronously with the radiation pulse. Extreme ultraviolet radiation from the plasma spanned a wide spectral range with pronounced maximum centered at λ = 11 ± 1 nm while the free electron laser pulses were emitted at a wavelength of 32 nm. The power density of the focused plasma radiation was approximately 2 × 107 W/cm2 and was seven orders of magnitude lower compared with the focused free electron laser beam. Radiation fluences in both experimental conditions were comparable. Despite quite different spectral characteristics and extremely different power densities, emission spectra of both photo-ionized plasmas consist of the same spectral lines within a wavelength range of 20 to 50 nm, however, with different relative intensities of the corresponding lines. The dominating spectral lines originated from singly charged ions (Ne II); however, Ne III lines were also detected. Additionally, computer simulations of the emission spectra, obtained for photo-ionized plasmas, driven by the plasma extreme ultraviolet source, were performed. The corresponding measured and calculated spectra are presented. An electron temperature and ionic composition were estimated. Differences between the experimental spectra, obtained for both irradiation conditions, were analyzed. The differences were attributed mainly to different energies of driving photons.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2013 

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