Argon metastable dynamics in a filamentary jet micro-discharge at atmospheric pressure

• Published in: Plasma sources science & technology 2012-06, Vol.21 (3), p.34002-1-8
• Main Authors: Niermann, B, Reuter, R, Kuschel, T, Benedikt, J, Böke, M, Winter, J
• Format: Article
• Language: English
• Subjects: Atmospheric pressure; Barometric pressure; Density; Dynamics; Electric discharges; Electrodes; Filaments; Metastable atoms
• ISSN: 0963-0252; 1361-6595
• DOI: 10.1088/0963-0252/21/3/034002

Space- and time-resolved measurements of Ar (3P2) metastable atoms at the exit of an atmospheric pressure radio-frequency micro-plasma jet are performed using tunable diode laser absorption spectroscopy. The discharge features a coaxial geometry with a hollow capillary as the inner electrode and a ceramic tube with a metal ring as the outer electrode. Absorption profiles of metastable atoms and optical emission measurements reveal the dynamics and the filamentary structure of the discharge. Single filaments with a diameter of 125 µm and metastable densities of about 1013 cm−3 are observed. The average spatial distribution of Ar metastables is characterized with and without a target in front of the jet, showing that the target potential and, therewith, the electric field distribution substantially change the filaments' expansion. Together with a detailed analysis of the ignition phase and the discharge's behavior under pulsed operation, the results give an insight into the excitation and de-excitation mechanisms.