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Title: Theory and analysis of operating modes in microplasmas assisted by field emitting cathodes

Motivated by the recent interest in the development of novel diamond-based cathodes, we study microplasmas assisted by field emitting cathodes with large field enhancement factors using a simplified model and comparisons with particle-in-cell with Monte Carlo collision (PIC-MCC) simulations and experiments. The model used to determine current-voltage characteristics assumes a linearly varying electric field in the sheath and predicts transition from an abnormal glow to arc mode at moderate current densities in a 1 mm argon gap. The influence of an external circuit is also considered to show the dependence of current as a function of the applied voltage, including potential drop across external resistors. PIC-MCC simulations confirm the validity of the model and also show the significant non-equilibrium nature of these low-temperature microplasmas with electron temperatures ∼1 eV and ion temperatures ∼0.07 eV in the quasi-neutral region. The model is also used to explain experimental data reported for a 1 mm argon gap at a pressure of 2 Torr using three different diamond-based cathodes with superior field emitting properties. The comparison shows that operating conditions in the experiments may not result in significant field emission and the differences observed in current-voltage characteristics can be attributed to small differences in the secondary electron emission coefficientmore » of the three cathodes. However, the model and simulations clearly indicate that field emission using novel cathodes with high field enhancement factors can be used to enhance microplasmas by significantly decreasing the power requirements to achieve a given plasma number density even in gaps at which field emission is traditionally not considered to be a dominant mechanism.« less
Authors:
 [1]
  1. School of Engineering, University of California, Merced, Merced, California 95343 (United States)
Publication Date:
OSTI Identifier:
22410422
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ARGON; CATHODES; COLD PLASMA; COLLISIONS; CURRENT DENSITY; DIAMONDS; ELECTRIC FIELDS; ELECTRIC POTENTIAL; ELECTRON EMISSION; ELECTRON TEMPERATURE; EXPERIMENTAL DATA; FIELD EMISSION; MONTE CARLO METHOD; PLASMA DENSITY; RESISTORS