Pressure scaling effects on a nanosecond range diffuse discharge in air

A positive high voltage and short nanosecond range pulse is applied between a pin electrode and a grounded plane to generate a large and diffuse discharge in air. The plasma which is induced is promising for applications such as ignition thanks to its homogeneity, its space extension, the energy levels which can be reached and the induced chemical reactivity. However, as pressure increases, these properties are no more satisfied since the discharge becomes filamentary and constricted, and easily tends to a thermal state which is dissipative and therefore less interesting. The purpose of this study is to investigate the limits of existence of the diffuse discharge with pressures ranging between 1 and 10 bars, considering similarity rules and pressure scaling effects on the dynamics of the discharge. Changing the distance between the electrodes and adjusting the pulse length and the voltage according to pressure are the ways to control this diffuse regime. Time resolved imaging, current and voltage measurements and emission spectroscopy are used to carry out this work.