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Streamer Corona Discharge Induced by Laser Pulses During LIF Measurements in a DC Non-thermal Plasma Reactor for NO Oxidation

Abstract A possible interference of the light emitted by the laser induced streamer coronas and the laser induced fluorescence (LIF) signal during the measurements of NO concentration in a DC positive corona discharge was experimentally investigated. For in-situ NO measurement a LIF system consisting of a XeF excimer laser, dye laser and BBO crystal, generating a tuned laser line at 226 nm was employed. From the measured occurrence timing between the regular streamer coronas, laser pulse, LIF signal and laser induced streamer it was found that the LIF signal appears almost immediately after the laser incidence and lasts over about 30 ns, while the induced streamer starts about 35 ns after the LIF signal and lasts about 350-500 ns. Due to the 5 ns interval between the LIF signal and the laser induced streamer the undisturbed detection of the LIF signal can be possible with a properly adjusted timing of the ICCD camera (the gate opening and exposure time). Two-dimensional distribution of NO molecules concentration in the discharge gap was measured using the LIF technique. The time-resolved evolution of the laser induced streamers was visualized using the ICCD camera with the proper timing adjustment. This resulted in determining the velocity of propagation of the streamer (about 2.5 × 105 m/s) and the averaged diameters of the leader channel and leader streamers (200 μm and 100 μm, respectively).