Multidimensional short-pulse space-charge-limited flow

Journal Article · Thu Jun 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2208086· OSTI ID:20787385

Koh, W S; Ang, L K; Kwan, T J.T. ^[1]

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1. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

The two-dimensional models of the space-charge-limited (SCL) current density at the short pulse limit for which the electron pulse length is comparable or smaller than the electron transit time across the gap (i.e., X{sub CL}{<=}1) have been developed. In particular, the scaling laws for short-pulse SCL electron emission in a planar diode with a circular emitting strip and a cylindrical diode with a finite length have been obtained and verified with particle-in-cell simulation. It is found that the enhancement (in terms of the long-pulse SCL current density) is proportional to X{sub CL}{sup -1} for small X{sub CL} for both planar and cylindrical cases. The enhancement of the cylindrical short-pulse SCL current density is also found to be larger for the convergent flow (cathode outside) than divergent flow (cathode inside). Multidimensional effects are important only for small emitting strips with size comparable to the effective penetration distance (into the gap) of the short-pulse electron beam. Smooth transition between the short-pulse regime and the long pulse (steady-state) regime is demonstrated.

• OSTI ID: 20787385
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 6 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAM-PLASMA SYSTEMS
CATHODES
CURRENT DENSITY
CYLINDRICAL CONFIGURATION
ELECTRON BEAMS
ELECTRON EMISSION
ELECTRONS
PLASMA
PLASMA SIMULATION
PULSES
RADIATION TRANSPORT
SCALING LAWS
SPACE CHARGE
STEADY-STATE CONDITIONS
THERMIONIC DIODES
TWO-DIMENSIONAL CALCULATIONS