Bonn 2000 – scientific programme

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P: Plasmaphysik

P 16: Plasmadiagnostik (Poster)

P 16.20: Poster

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

Time-resolved probe diagnostics in a pulsed microwave discharge containing hydrogen — •N. Lang¹, J. Röpcke¹, E. Teboul², and A. Rousseau² — ¹Institut für Niedertemperatur-Plasmaphysik, Greifswald, Germany — ²Laboratoire de Physique des Gaz et des Plasmas, CNRS, F 91405 Orsay, France

Methods of emission spectroscopy (OES) can only provide information about population densities of excited particles. But for a detailed balancing of the neutral kinetic the knowledge of the electron density and its energy distribution is necessary. In this contribution in addition to OES investigations results of time-resolved probe measurements in a pulsed microwave plasma(2.45 GHz) containing hydrogen will be presented. The incoupled microwave power was modulated with rectangular pulses in a range of 600 W to 3.6 kW. The pulse width was 1 ms, the duration between two pulses 50 ms. The electron density and the electron temperature were determined in axial and radial direction of the active plasma zone with coaxial Langmuir probes. A time resolution of 30 µ s was achieved. For the analysis of the probe characteristics the collisional theory of Zakrzweski [1] was used, i.e. changes of the ionic current due to collisions between ions and neutrals in the sheath were taken into account. For a pressure of 55 Pa the time evolution of the electron density showed an increasing to a stationary value 2.7 · 10¹¹ cm⁻³ within the first 200 µ s. The electron temperature relaxed from 8 eV during the breakdown to 6 eV at the end of the pulse.

[1] Z.Zakrzewski et al, Plasma Phys. 16 (1974), pp.1195.