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P: Fachverband Plasmaphysik

P 22: Niedertemperaturplasmen II

P 22.2: Talk

Friday, March 1, 2013, 10:15–10:30, HS 2

Determination of plasma densities in noble gas discharges by THz Time Domain Spectroscopy — •Steffen Marius Meier, Tsanko Vaskov Tsankov, Dirk Luggenhölscher, and Uwe Czarnetzki — Institute for Atomic and Plasma Physics, Ruhr-University Bochum, Germany

Terahertz Time Domain Spectroscopy (THz TDS) is a spectroscopic method which is widely used in many scientific fields. It combines the advantages of short pico-second electromagnetic pulses and a broad spectrum in the THz range. In plasma physics these properties allow determining the complex dispersion function of a plasma as well as the plasma density and the collision frequency.

Using this diagnostic method the plasma densities of discharges in noble gases (He, Ne, Ar, Kr, Xe) are measured as a function of the power in a magnetic multi-pole ICP discharge [1,2]. Densities as high as 10¹⁴ cm⁻³ are obtained at a filling gas pressure of 20 Pa. An analytical model is developed to explain the obtained non-linear power-density variation. The satisfactory agreement between model and measurements indicates that neutral gas depletion effects due to high gas temperatures and non-negligible electron pressure become important.

[1] Maurmann, S.; Drepper, P.; Ferri, S.; Petershagen, N., A magnetic multipole plasma source for the investigation of electron-atom collision processes, Contrib. Plasma Phys. 40, (2000), 152–157

[2] Babkina, T. M., Generation of hyperthermal atoms through surface neutralisation, PhD Thesis, Ruhr-Universität Bochum (2006)