Space-charge sheath 6 Average field 4 Biasing voltages 4 Breakdown threshold 4 Carrier concentration 4 Cold ions 4 Cutting torch 4 Drift diffusion 4 Electric fields 4 Electric potential 4 Electron densities 4 Electron density measurement 4 Electron temperature 4 Fluid dynamics 4 Gas breakdown 4 Hydrodynamic model 4 Ion collisions 4 Ion density 4 Ion velocity 4 Ions 4 Mean-free path 4 Momentum equation 4 Nozzle exits 4 Nozzle wall 4 Nozzles 4 Numerical studies 4 Plasma edges 4 Plasma turbulence 4 Poisson equation 4 Poisson's equation 4