The Evolution of the Optical Emission Pattern of a Nanosecond Pulsed Helium Microdischarge With a Pin-to-Pin Electrode at Atmospheric Pressure

The evolution of a nanosecond pulsed microdischarge with a pin-to-pin electrode configuration in atmospheric pressure helium is obtained using the spatially and temporally resolved optical emission measurement. Three phases of the discharge mode are identified: 1) the establishment of the discharge channel, evidenced by the propagation of the emission from the high voltage electrode to the ground electrode in the breakdown phase; 2) the expansion of the discharge region around the ground electrode in the discharge phase; and 3) the shrinkage of the discharge region into a cylindrical-shape and the decay of the emission in the afterglow phase.