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Augsburg 2006 – scientific programme

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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

Wednesday, March 29, 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 Thiele11Institut 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).

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