Berlin 2005 – wissenschaftliches Programm
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P: Plasmaphysik
P 7: Poster: Niedertemperaturplasmen / Plasmatechnologie 3, Diagnostik 3
P 7.19: Poster
Freitag, 4. März 2005, 16:30–18:30, Poster HU
Line-integrated electron density measurements in a low-temperature argon plasma by the nested-cavity FIR laser interferometer — •Carsten Pargmann, Vikram Singh, Philipp Kempkes, and Henning Soltwisch — Institut für Experimentalphysik V, Ruhr-Universität Bochum
Line-integrated electron densities in low-temperature rf discharge plasmas are commonly measured with microwave interferometers. In order to increase the spatial resolution, an optically pumped far infrared (FIR) laser is used as a radiation source. Because the sensitivity decreases with decreasing wavelength, a nested cavity FIR laser interferometer was developed. The FIR beam leaves the laser cavity through an outcoupling hole and is reflected back by an external mirror. The laser power changes in a nonlinear way with the distance of the external mirror (or with changes of the refractive index of a plasma) and can be monitored behind a hole in the external mirror. The measurements are performed with a wavelength of 432.6 µm in an inductively coupled GEC reference cell filled with argon. The detection limit of the line-integrated electron density is 1012 cm−2. The results are compared to radial scans of Langmuir probe measurements.