Trichel pulse in various gases and the key factor for its formation

We confirm in this paper that Trichel pulse of negative corona is a common phenomenon that can occur in various gases rather than only in electronegative gases as considered in the last 70 years since G W Trichel firstly reported. Trichel pulse is exactly a mode transition between low-current Townsend and high-current normal glow regime, two pulseless stages of negative corona with different operating conditions and ion flux threshold. The rising of the pulse corresponds to the breakdown and formation of temporal glow discharge, the decay corresponds to the destroy of temporal sheath, and the interval (or repetition frequency of pulses) is determined by the re-building of the positive ion cloud to enhance significantly the local electric field for glow discharge to form again. The positive ions play a predominant role for the pulse formation and the mode transition, while the negative ions in electronegative gas are not necessary even if they affect greatly the pulsing process.