Breakdown development in a nanosecond pulsed dielectric barrier discharge in humid air in plane-to-plane geometry

We used the ns Electric Field Induced Second Harmonic (EFISH) generation diagnostic to measure the electric field evolution in a200 ns pulse, dielectric barrier, plane-to-plane discharge in humid air, on the time scale shorter than the laser pulse duration. Plasmaimaging by an ICCD camera detected a uniform evolution of the discharge emission during the breakdown. Spectroscopicmeasurements tracked the N2 second positive and first negative systems to infer the reduced electric field (E/N) evolution. EFISH measurements showed the electric field persistent during the entire HV pulse, with the residual field between pulses and the fieldinversion at the start and end of the HV pulse. The experimental data are consistent with the simulations, with the electron attachmentand negative ion kinetics incorporated. The modelling predictions indicate that the rapid electron density decay due to attachmentand recombination is the dominant factor sustaining the electric field in the plasma after breakdown. Spectroscopic E/N determination showed the time evolution at variance with the EFISH measurements, which may be due to the electron attachmentand non-locality of the EEDF. Possible explanations are discussed.