Abstract
High-voltage pulse discharge experiments in helium [Bokhan et al, 2013 Phys. Plasmas 20(3) 033507] showed a possibility to control the electron avalanche development on a subnanosecond timescale. The controlled current growth rate was of 500 A/(cm2ns) for an applied voltage of 20 kV and gas pressure of 6 Torr. Here, a kinetic model of the breakdown is developed to analyze the mechanism of current growth, which takes into account the kinetics of electrons, ions, fast atoms and photons with a Doppler shift (DS). Using particle in cell simulations, we show a critical role of DS photons in the secondary electron emission during the breakdown. DS photons appear in discharge due to a) electronic excitations in the background gas by heavy particles (ions and fast atoms) and b) in collisional excitation transfer reactions between fast atoms (He_f) and atoms excited by electron impact (He^*), He_f + He^* = He_f^* + He. The latter, newly analysed, mechanism is dominant in the DS photons production during the breakdown in high-voltage pulse discharges. Our experimental and calculation results show a decrease of the breakdown timescale with increasing gas pressure from 6 Torr to 20 Torr.

Bio
Dr. Irina Schweigert is Leading Scientist at Khristianovich Institute of Theoretical and Applied Mechanics (ITAM) and a visiting researcher at George Washington University. She has a BS in Physics from Novosibirsk State University and PhD in Physics and Applied Mathematics from ITAM. Her research interests are in low temperature plasma, discharges, processing plasma, dusty plasmas, electron energy distribution function, kinetic simulation with particle-in-cell Monte Carlo collision method, molecular dynamic simulation, strongly-coupled system, condensed matter: melting and structural transitions, transport.

Please see the Colloquium Announcement for more details.