Augsburg 2006 – scientific programme
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P: Plasmaphysik
P 33: Diagnostik 4
P 33.3: Talk
Thursday, March 30, 2006, 11:45–12:00, 1002
Electron density measurements in reactive low-temperature plasmas by means of a simple far-infrared laser interferometer — •Carsten Pargmann1, Shailendra Vikram Singh2, Phillipp Kempkes1, and Henning Soltwisch1 — 1Ruhr-Universität Bochum — 2TU Eindhoven
A simple and sensitive far-infrared (fir) laser interferometer is described and its application to reactive low-temperature plasmas is shown. The fir beam leaves the resonator of an optically pumped fir laser through a coupling hole in the end mirror and is reflected back into the cavity by an external mirror. The output intensity of the laser undergoes strong nonlinear variations, if the optical distance of the external mirror is changed. The power variation is monitored through a small opening in the external mirror. A wavelength of 432.6 µ m and a Schottky-diode detector yield a minimum detectable change of the line-integrated electron density of about 3· 1015 m−2. Measurements in an inductively coupled rf discharge filled with argon, methane and oxygen have been made and the very good time resolution is demonstrated by switching the discharge between the E- and the H-mode. Whenever possible the results have been compared to Langmuir probe measurements.