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Acta Physica Slovaca 63, No.3, 105 – 205 (2013) (101 pages)
THE BREAKDOWN MECHANISMS IN ELECTRICAL DISCHARGES: THE ROLE OF THE FIELD EMISSION EFFECT IN DIRECT CURRENT DISCHARGES IN MICROGAPS M. Radmilović-Radjenović1, B. Radjenović1, M. Klas2, A. Bojarov1 and Š. Matejčik2 1Institute of Physics, University of Belgrade, Pregrevica 118, 110 80 Belgrade, Serbia 2Department of Experimental Physics, Comenius University, Mlynská dolina F2, 842 48 Bratislava, Slovakia Full text: ::pdf :: (Received 17 March 2014, accepted 19 March 2014) Abstract: This review represents an attempt to sum up the current state of the research in the field of breakdown phenomena in electrical discharges. The paper provides facts and theories concerning different classes of direct current, radio and microwave frequency discharges, in vacuum, in the gas and in liquids, without and in the presence of the magnetic fields. The emphasize was made on the field emission effects and on the fundamental aspects of the breakdown phenomena in microdischarges via discussions and analysis of the experimental, theoretical and simulation results. It was found that the Paschen’s law is not applicable for the micron gap sizes, when deviations from the standard scaling law become evident and modified Paschen curve should be used. The explanation of the deviations from the Paschen law was attributed to the secondary electron emission enhanced by the strong field generated in microgaps. The experiments were carried out in order to establish scaling law in microgaps. The volt-ampere characteristics were also recorded and compared with the theoretical predictions based on the Fowler-Nordheim theory. The importance of the enhancement factor and the space charge on results was also considered. On the basis of the experimental breakdown voltage curves, the effective yields in microgaps have been estimated for different gases which can be served as input data in modeling. The effective yields allow analytically produce modified Paschen curves that predicts the deviations from the Paschen law observed in the experiments. In addition, we present results of computer simulations using a Particle-in-cell/Monte Carlo Collisions (PIC/MCC) code with the secondary emission model in order to include the field emission enhanced secondary electron production in microgaps. The agreement between simulation and experimental results suggest that computer simulations can be used to improve understanding of the plasma physics as an alternative to analytical models and to the laboratory experiments. Apart from their theoretical importance, the results reviewed in this paper could be useful for determining the minimum ignition voltages in microplasma sources as well as the maximum safe operating voltages and critical dimensions in different microdevices. Finally, the understanding of the scaling may play a crucial role in developing models of micro-discharges and applications. DOI: 10.2478/apsrt-2013-0003 PACS: 51.50,+v, 52.80.-s, 52.65.Rr Keywords: Electrical discharges, Breakdown, Microdischarges, Field emission |
ISSN 1336-040X (online) ISSN 0323-0465 (printed) For authors: ActaStyle.cls |
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