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Title: Two-dimensional space-charge-limited flows in a crossed-field gap

Abstract

This letter presents a two-dimensional (2D) model of space-charge-limited current in a planar crossed-field gap with a magnetic strength of B/B{sub H}=0-3, where B{sub H} is the Hull cutoff magnetic field. The electrons are emitted from an infinite length strip of finite width W comparable to the gap spacing D. It is found that the 2D enhancement of the crossed-field limiting current is 1+Fx4D/({pi}W), where F (=0.05-0.5) is a normalized mean-position factor, and it is a function of B/B{sub H}. Good agreement has been obtained in comparisons with particle-in-cell simulation.

Authors:
;  [1]
  1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore and Institute of High Performance Computing, Singapore 117528 (Singapore)
Publication Date:
OSTI Identifier:
20960192
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 14; Other Information: DOI: 10.1063/1.2720710; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COMPARATIVE EVALUATIONS; CROSSED FIELDS; ELECTRON EMISSION; ELECTRONS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA SIMULATION; SPACE CHARGE; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Koh, W. S., and Ang, L. K. Two-dimensional space-charge-limited flows in a crossed-field gap. United States: N. p., 2007. Web. doi:10.1063/1.2720710.
Koh, W. S., & Ang, L. K. Two-dimensional space-charge-limited flows in a crossed-field gap. United States. doi:10.1063/1.2720710.
Koh, W. S., and Ang, L. K. Mon . "Two-dimensional space-charge-limited flows in a crossed-field gap". United States. doi:10.1063/1.2720710.
@article{osti_20960192,
title = {Two-dimensional space-charge-limited flows in a crossed-field gap},
author = {Koh, W. S. and Ang, L. K.},
abstractNote = {This letter presents a two-dimensional (2D) model of space-charge-limited current in a planar crossed-field gap with a magnetic strength of B/B{sub H}=0-3, where B{sub H} is the Hull cutoff magnetic field. The electrons are emitted from an infinite length strip of finite width W comparable to the gap spacing D. It is found that the 2D enhancement of the crossed-field limiting current is 1+Fx4D/({pi}W), where F (=0.05-0.5) is a normalized mean-position factor, and it is a function of B/B{sub H}. Good agreement has been obtained in comparisons with particle-in-cell simulation.},
doi = {10.1063/1.2720710},
journal = {Applied Physics Letters},
number = 14,
volume = 90,
place = {United States},
year = {Mon Apr 02 00:00:00 EDT 2007},
month = {Mon Apr 02 00:00:00 EDT 2007}
}
  • A fully kinetic model for the electron flow in a crossed field device is derived and used to determine the system stationary states. It is found that for low injection temperatures, there is a simultaneous presence of distinct stationary solutions and an abrupt transition between accelerating and space-charge limited regimes. On the other hand, for high injection temperatures, there is only a single stationary solution branch and the change between the regimes becomes continuous. For intermediate temperatures, it is then identified a critical point that separates the abrupt and continuous behaviors. It is also investigated how intrinsic space-charge oscillations maymore » drive stationary states unstable in certain parameter regimes. The results are verified with N-particle self-consistent simulations.« less
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  • In this paper, the space-charge-limited (SCL) electron flows in a drift space is studied by including the effect of finite electron pulse length, which is smaller than the gap transit time. Analytical formulas are derived to calculate the maximum SCL current density that can be transported across a drift space under the short-pulse injection condition. For a given voltage or injection energy, the maximum current density that can be transported is enhanced by a large factor (as compared to the long-pulse or steady-state case), and the enhancement is inversely proportional to the electron pulse length. In drift space, the effectmore » of pulse expansion is important at very short-pulse length, and the short-pulse enhancement factor is smaller as compared to a diode. The enhancement factor will be suppressed when the injection energy is larger than the electron rest mass, and effect of pulse expansion is less critical at relativistic energy. The analytical formulas have been verified by performing a particle-in-cell simulation in the electrostatic mode.« less