Transition from Fowler-Nordheim field emission to space charge limited current density

Journal Article · Sat Jul 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2226977· OSTI ID:20860145

Feng, Y; Verboncoeur, J P ^[1]

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1. 4167 Etcheverry Hall, Department of Nuclear Engineering, University of California at Berkeley, Berkeley, California 94720-1730 (United States)

The Fowler-Nordheim law gives the current density extracted from a surface under strong fields, by treating the emission of electrons from a metal-vacuum interface in the presence of an electric field normal to the surface as a quantum mechanical tunneling process. Child's law predicts the maximum transmitted current density by considering the space charge effect. When the electric field becomes high enough, the emitted current density will be limited by Child's law. This work analyzes the transition of the transmitted current density from the Fowler-Nordheim law to Child's law space charge limit using a one-dimensional particle-in-cell code. Also studied is the response of the emission model to strong electric fields near the transition point. We find the transition without geometrical effort is smooth and much slower than reported previously [J. P. Barbour, W. W. Dolan, J. K. Trolan, E. E. Martin, and W. P. Dyke, Phys. Rev. 92, 45 (1953)]. We analyze the effects of geometric field enhancement and work function on the transition. Using our previous model for effective field enhancement [Y. Feng and J. P. Verboncoeur, Phys. Plasmas 12, 103301 (2005)], we find the geometric effect dominates, and enhancement {beta}>10 can accelerate the approach to the space charge limit at practical electric field. A damped oscillation near the local plasma frequency is observed in the transient system response.

• OSTI ID: 20860145
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CURRENT DENSITY
ELECTRIC FIELDS
ELECTRONS
FIELD EMISSION
LANGMUIR FREQUENCY
ONE-DIMENSIONAL CALCULATIONS
PLASMA
PLASMA SIMULATION
PLASMA WAVES
QUANTUM MECHANICS
RADIATION TRANSPORT
SPACE CHARGE
SURFACES
TRANSIENTS
TUNNEL EFFECT
WORK FUNCTIONS