Augsburg 2006 – wissenschaftliches Programm
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P: Plasmaphysik
P 28: Astrophysikalische Plasmen; Dichte Plasmen 1; Schwerionen- und lasererzeugte Plasmen 2; Staubige Plasmen 4; Theorie 1
P 28.13: Poster
Mittwoch, 29. März 2006, 17:30–19:00, Flure
Bremsstrahlung vs. Thomson scattering in VUV-FEL plasma experiments — •Carsten Fortmann1, Ronald Redmer1, Heidi Reinholz1, Gerd Röpke1, Wojziech Rozmus2, Volker Schwarz1, and Robert Thiele1 — 1Institut für Physik, Universität Rostock — 2Department of Physics, University of Alberta, Edmonton
Thomson scattering is a powerful diagnostic tool
for highly ionized dense plasmas.
It will be used in VUV-FEL experiments at DESY to
determine plasma parameters, such as density and temperature.
On the other hand,
thermal bremsstrahlung photons from the plasma
form a non negligible background which has to be overcome by
the Thomson signal.
Thus, it is crucial to determine experimental
conditions where the Thomson scattering signal is
dominant against bremsstrahlung.
This problem has so far
been investigated by using classical
expressions for the bremsstrahlung spectrum [1].
In this work, the bremsstrahlung
spectrum is derived from linear response theory
in a systematic manner [2].
Medium effects, such as screening and strong collisions,
are accounted for. Thereby,
we improve the standard formulas for bremsstrahlung used
in previous works and provide a basis for
future Thomson scattering experiments, e.g.
the determination of threshold laser intensities.
We show that the account of medium effects
leads to larger threshold intensities as
compared to previous work.
[1] H. A. Baldis, J. Dunn, and W. Rozmus. Rev. Sci. Inst. 73, 4223 (2002).
[2] C. Fortmann, R. Redmer, H. Reinholz, G. Röpke, W. Rozmus, V. Schwarz, and R. Thiele (in preparation).