EFISH Electric-field measurement in discharges relevant to plasma-assisted-combustion

We present quantitative time- and space-resolved electric-field measurements in atmospheric-pressure nanosecond repetitively pulsed (NRP) discharges. Discharges are formed in a plasma-assisted-combustion burner, developing across a flame-front, partially in a fresh lean methane-air mixture and partially in the burned gases. The electric field has a prominent role in determining the reaction rate for electron impact reactions, so the knowledge of its space and time evolution would be advantageous for numerical simulations. The Electric-Field-Induced Second-Harmonic generation (EFISH) technique was used in the measurements. Spatially resolved measurements are obtained by raster scanning. Two significant challenges are (1) the small spatial features of the electric field in this kind of discharges and (2) the presence of different gases that alter the EFISH generation. A novel deconvolution-like post-processing procedure is used to improve the spatial resolution, overcoming the limitations arising from a large interaction volume, typical in EFISH measurements. Preliminary results suggest a first ionization wave (from anode to cathode) and a return wave. Evolution of the electric field close to the anode is analyzed and discussed.