Berlin 2001 – wissenschaftliches Programm
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A: Atomphysik
A 10: Posters Wednesday (Cooling and Trapping, Electron Scattering and Recombination)
A 10.24: Poster
Mittwoch, 4. April 2001, 12:30–15:00, AT3
EUV spectroscopy of highly charged tungsten ions relevant to hot plasmas — •Christoph Biedermann1, Gerd Fußmann1, Pinhas Mandelbaum2, Rainer Radtke1, and Jean-Louis Schwob2 — 1Max-Planck-Institut für Plasmaphysik, Bereich Plasmadiagnostik, EURATOM Association, D-10117 Berlin, Germany — 2Racah Institute of Physics, The Hebrew University, 91904 Jerusalem, Israel
The radiation from tungsten ions produced with the Berlin Electron Beam Ion Trap (EBIT) was investigated in the extreme ultraviolet spectral region using a 2-m grazing-incidence spectrometer. By operating EBIT at electron beam energies between 500 eV and 4 keV tungsten in charge states ranging from I-like W21+ to Cu-like W45+ are selectively excited. Lines of Sr- to Cu-like tungsten were identified. For ionization stages below Sr-like W36+ a bright emission band of about 2 Å width was observed, which shifts from 54 to 50 Å when lowering the charge state. The band of unresolved lines originates from 4l − 4l′ transitions of ions with an open 4d subshell. Calculations using the atomic structure code package HULLAC demonstrate that the narrowing and shift of the band emission can be understood in the framework of the unresolved transition array using mixed configurations. The theoretical analysis of the spectrum employs detailed calculations based on a collisional-radiative model to account for the low electron density in EBIT and reproduces the variations of the observed emission pattern. These results may help to explain the unresolved broad emission feature around 50 Å observed in the impurity spectrum from tokamak-produced plasmas.