Spatial and Temporal Distribution of Microplasma in Small Discharge Gaps

Emission spectra were measured by the use of an intensified charge coupled device (ICCD) camera and a spectrometer to which was attached a fiber optic. Photographs of microdischarges were taken using a microscope, a digital camera, and an ICCD high-speed camera. A self-made fiber optic with a 100-μm diameter was used in order to have an accurate measurement of a small part of the microplasma discharge. A negative-pulse Marx generator was used to energize the electrodes. Experiments were carried out at atmospheric pressure in Ar and N₂/Ar mixture. The discharge voltage was a negative pulse, the rise time was 100 ns, and the width was 1 μs at 1 kHz. The electrodes used had 3-mm hole diameter, and the discharge gap was set at 100 μm. Microplasma was measured in different points along the discharge gap. The spatial and temporal distribution showed characteristics that suggested the microplasma formation and its evolution across the discharge gap.