Plasma fluctuations 6 Arc plasma 4 Cutting torch 4 Dynamics 4 Experimental observation 4 Insulating film 4 Ion-current signal 4 Non destructive 4 Nonequilibrium plasmas 4 Nozzle orifice 4 Nozzle wall 4 Nozzles 4 Oxygen cutting 4 Plasma diagnostics 4 Plasma dynamics 4 Plasmas 4 Power supply 4 Space charges 4 Steady state 4 Collision-free plasma 2 Electron currents 2 Electron temperature 2 Exponential expression 2 Fluctuation analysis 2 Ionization 2 Langmuir probe diagnostics 2 Langmuir probe measurements 2 Langmuir probes 2 Local thermal equilibrium 2 Probes 2