Electron heating in atmospheric pressure glow discharges

The application of nanosecond voltage pulses to weakly ionized atmospheric pressure plasmas allows heating the electrons without considerably increasi ng the gas temperature, provided that the duration of the pulses is less th an the critical time for the development of glow-to-arc transitions. The sh ift in the electron energy distribution towards higher energies causes a te mporary increase in the ionization rate, and consequently a strong rise in electron density. This increase in electron density is reflected in an incr eased decay time of the plasma after the pulse application. Experiments in atmospheric pressure air glow discharges with gas temperatures of approxima tely 2000 K have been performed to explore the electron heating effect. Mea surements of the temporal development of the voltage across the discharge a nd the optical emission in the visible after applying a 10 ns high voltage pulse to a weakly ionized steady state plasma demonstrated increasing plasm a decay times from tens of nanoseconds to microseconds when the pulsed elec tric field was raised from 10 to 40 kV/cm. Temporally resolved photographs of the discharge have shown that the plasma column expands during this proc ess. The nonlinear electron heating effect can be used to reduce the power consumption in a repetitively operated air plasma considerably compared to a dc plasma operation. Besides allowing power reduction, pulsed electron he ating also has the potential to enhance plasma processes, which require ele vated electron energies, such as excimer generation for ultraviolet lamps. (C) 2001 American Institute of Physics.