Understanding discharge inception in air using high-voltage experiments and particle-in-cell simulations*

Understanding discharge inception is important for fields like lightning research, lightning protection, and high-voltage technology. In this study, the inception times and probabilities of discharges are measured in a vessel filled with dry and humid air between 100 and 1000 mbar. A pin-to-plate electrode geometry is considered, in which tens of kV are applied over a cm-scale gap. The inception time is defined as the moment a photomultiplier tube measures a signal above the background noise. The inception probabilities and spread of inception times are compared to Monte-Carlo particle simulations with different initial charge densities (e-, and O2-) to find conditions that reproduce the statistics from the experiments.\\ \\ Preliminary results show two distinct inception timescales: tens of ns, and hundreds of ns. In the first case the electrons have a high probability of reaching the electrode without getting attached while in the second case negative ions 'transport' the electrons to the high field region. From the high-voltage experiments and simulations, we can estimate the initial charge densities and species in the vessel.