Thermal instability and volume contraction in a pulsed microwave N₂ plasma at sub-atmospheric pressure

Abstract We studied the evolution of an isolated pulsed plasma in a vortex flow stabilised microwave (MW) discharge N 2 at 25 mbar via combination 0D kinetics modelling, iCCD imaging and laser scattering diagnostics. Quenching electronically excited results fast gas heating onset thermal-ionisation instability, contracting volume. The instability driven by vibrational excitation pathways is found to facilitate significantly higher conversion (i.e. dissociation atomic ) compared pre-instability conditions, emphasizing potential utility this dynamic future fixation applications. be instigated super-elastic electron energy distribution tail vibrationally . Radial contraction skin depth occur post while axial elongation temporarily contracted during thermal onset. An increase power reflection eventually limits destabilising effects exothermic quenching. Translational temperature reach quasi-non-equilibrium after contraction, with translational temperatures reaching ?1200 K pulse end, are near equilibrium (1 eV, or ?11 600 K). This first description importance quenching instabilities gives additional fundamental understanding behaviour MW context, thereby brings eventual implementation novel method one step closer.