Bonn 2000 – scientific programme

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P: Plasmaphysik

P 16: Plasmadiagnostik (Poster)

P 16.6: Poster

Wednesday, April 5, 2000, 10:30–13:00, Aula

Investigation of the contribution of electron-atom collisions to the Redistribution of Radiation in a helium plasma — •S. Ferri, P. Drepper, S. Maurmann und H.-J. Kunze — Institut für Experimentalphysik V, Ruhr-Universität Bochum

In plasmas where kinetics are such that electron-atom collisions dominate all other excitation processes, redistribution of radiation can be observed, that is photons absorbed at a given frequency can result in additional fluorescence from a dipole allowed transition. Such conditions are reached in a Magnetic Multipole Plasma Source, where electron temperatures in a range of 0.3 eV ≤ kT_e≤ 5 eV and electron densities in a range of 10¹¹ cm⁻³≤ n_e≤ 10¹³ cm⁻³ at filling pressures of helium 1 Pa ≤ p_g ≤ 5 Pa are achieved. In the present study, Rayleigh scattering and redistribution of radiation of dipole allowed transitions of helium triplet levels are investigated both experimentally and theoretically. We present comparisons between the experimental data and the two-photon line shapes calculated by a Radiative Redistribution Model that lead to a measure of the electron-atom collision rates of upper states of HeI.