Spatiotemporal dynamics of nanosecond pulsed discharge in the form of a fast ionization wave: self-consistent two-dimensional modeling and comparison with experiments under negative and positive polarity

Nanosecond discharges are characterized by a shift in energy branching toward the excitation of electronic levels and dissociation, making them particularly attractive for plasma chemistry. Understanding the spatio-temporal structure of these discharges is especially important. This paper presents a detailed 2D-axisymmetric numerical analysis of a nanosecond discharge propagating in a long tube and in pure nitrogen. The modeling is conducted using a self-consistent plasma fluid solver under the local mean energy approximation, including photoionization. The discharge develops at moderate pressures, 1-10 Torr, in the form of a fast ionization wave (FIW). Simulations are performed for both negative and positive polarities of the voltage pulse applied to the high-voltage electrode. The computational results are validated against available experimental data, including FIW velocity within the studied pressure range, electron density, longitudinal electric field, and the radial distribution of N₂(C 3 Π u ) emission on a nanosecond timescale.