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P: Plasmaphysik
P 4: Diagnostics II
P 4.4: Talk
Tuesday, April 3, 2001, 17:15–17:30, 2032
TALIF-measurements of atomic nitrogen density in a pulsed microwave discharge — •T. Repsilber, M. Baeva, and J. Uhlenbusch — Institut für Laser– und Plasmaphysik, Heinrich–Heine–Universität, Düsseldorf
Absolutly calibrated time and space resolved density measurements of atomic nitrogen produced by a 20 Hz pulsed microwave discharge in pure nitrogen are presented. Typically the discharge is operated at pressures between 2.5 and 20 mbar with pulse durations of 50−500 µs. To diagnose the nitrogen atoms TALIF on the 207 nm transition is applied. For absolut calibration purposes the technique of NO titration in the afterglow of a flowtube reactor is employed. The approximations needed for this method of calibration are discussed. The generation and loss of particles in the approximately spherical plasma are described by a time-dependent numerical model, which takes into account the non-Maxwellian electron energy distribution and resulting rate coefficients of vibrational and electronical excitation as well as ionisation and formation of radicals. Thereby particular attention is payed to the molecular ion N4+ as dominant ionic species.