Properties of an atmospheric pressure radio-frequency argon and nitrogen plasma

An atmospheric pressure capacitive discharge source has been developed that operates at power densities over 100 W cm(-3). The ground state nitrogen atom concentration was measured at the exit of the source by titration with NO, and it was found to reach a maximum of 3.0 +/- 0.8 x 10(17) cm(-3) at 6.0 vol% N-2 in argon, 250 degrees C and 150 W cm(-3). This is equivalent to 2.3 vol% of N atoms in the afterglow. At these conditions, the electron density and temperature are estimated to be 3.1 x 10(12) cm(-3) and 1.2 eV. A plug-flow model of the plasma and afterglow was developed, and it was determined that the maximum N atom concentration achievable is limited by three body recombination.