skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A multi-dimensional Child–Langmuir law for any diode geometry

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/5.0071018· OSTI ID:1978980

While prior theoretical studies of multi-dimensional space-charge limited current (SCLC) assumed emission from a small patch on infinite electrodes, none have considered emission from an entire finite electrode. In this paper, we apply variational calculus (VC) and conformal mapping, which have previously been used to derive analytic solutions for SCLC density (SCLCD) for nonplanar one-dimensional geometries, to obtain mathematical relationships for any multi-dimensional macroscopic diode with finite cathode and anode. We first derive a universal mathematical relationship between space-charge limited potential and vacuum potential for any diode and apply this technique to determine SCLCD for an eccentric spherical diode. We then apply VC and the Schwartz–Christoffel transformation to derive an exact equation for SCLCD in a general two-dimensional planar geometry with emission from a finite emitter. Particle-in-cell simulations using VSim agreed within 4%–13% for a range of ratios of emitter width to gap distance using the thinnest electrodes practical for the memory constraints of our hardware, with the difference partially attributed to the theory's assumption of infinitesimally thin electrodes. After generalizing this approach to determine SCLCD for any orthogonal diode as a function of only the vacuum capacitance and vacuum potential, we derive an analytical formulation of the three-dimensional Child–Langmuir law for finite parallel rectangular and disk geometries. These results demonstrate the utility for calculating SCLCD for any diode geometry using vacuum capacitance and vacuum potential, which are readily obtainable for many diode geometries, to guide experiment and simulation development.

Research Organization:
Purdue Univ., West Lafayette, IN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES); US Air Force Office of Scientific Research (AFOSR)
Grant/Contract Number:
SC0018156; FA9550-18-1-0218; FA9550-19-1-0101
OSTI ID:
1978980
Alternate ID(s):
OSTI ID: 1833876
Journal Information:
Physics of Plasmas, Vol. 28, Issue 12; ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

References (63)

Novel Scaling Laws for the Langmuir-Blodgett Solutions in Cylindrical and Spherical Diodes journal June 2013
Space-Charge Effects in the Field-Assisted Thermionic Emission from Nonuniform Cathodes journal January 2021
Enhanced space charge limited current for curved electron emitters journal October 2020
A simple physical derivation of Child–Langmuir space-charge-limited emission using vacuum capacitance journal February 2005
Space‐charge‐limited current and capacitance in double‐junction diodes journal February 1987
Inertial confinement fusion: Review and perspective journal January 1984
High power microwave generation by a coaxial virtual cathode oscillator journal January 1999
Currents Limited by Space Charge between Concentric Spheres journal July 1924
Applying Conformal Mapping to Derive Analytical Solutions of Space-Charge-Limited Current Density for Various Geometries journal January 2021
Effect of space charge limited current on performance of organic field-effect transistors journal December 2018
Response to “Comment on ‘A coordinate system invariant formulation for space-charge limited current in vacuum’” [Appl. Phys. Lett. 118 , 266101 (2021)] journal June 2021
Edge Corrections for Strip and Disc Capacitors journal March 1985
Space-charge-limited current in a film journal June 1989
Space-charge-limited current in cylindrical diodes with finite-length emitter journal March 2002
Numerical solution of Fredholm integral equations of the second kind by using integral mean value theorem journal May 2011
Space-Charge Limited Current From a Finite Emitter in Nano- and Microdiodes journal January 2021
Space-charge and trap-filling effects in organic thin film field-effect transistors journal July 2004
The Effect of Space Charge and Residual Gases on Thermionic Currents in High Vacuum journal December 1913
Multidimensional short-pulse space-charge-limited flow journal June 2006
Space–charge limited current in nanodiodes: Ballistic, collisional, and dynamical effects journal March 2021
Modeling space-charge-limited currents in organic semiconductors: Extracting trap density and mobility journal November 2011
A new simple algorithm for space charge limited emission journal September 2020
Two-Dimensional Space-Charge-Limited Emission: Beam-Edge Characteristics and Applications journal September 2001
Approximate Solutions of the Space‐Charge Problem for Some Unusual Electrode Geometries journal December 1953
Currents Limited by Space Charge between Coaxial Cylinders journal October 1923
Space charge limited two-dimensional electron flow in a rectangular geometry journal July 2007
On the Space‐Charge‐Limited Current between Nonsymmetrical Electrodes journal August 1955
Three-dimensional Child–Langmuir law for uniform hot electron emission journal May 2005
Onset of space charge limited current for field emission from a single sharp tip journal March 2012
Space charge limited electron flow in two dimensions without magnetic field journal August 2011
Space-Charge-Limited Current Injection Into Free Space and Trap-Filled Solid journal July 2021
Two-dimensional analytical Mott-Gurney law for a trap-filled solid journal April 2007
The circular disk parallel plate capacitor journal December 1994
100 years of the physics of diodes journal March 2017
Space-Charge-Limited 2D Electron Flow between Two Flat Electrodes in a Strong Magnetic Field journal August 2003
A Set of Benchmark Tests for Validation of 3-D Particle in Cell Methods journal May 2021
Simple Theory for the Two-Dimensional Child-Langmuir Law journal December 2001
Inertial‐Electrostatic Confinement of Ionized Fusion Gases journal October 1967
Non-uniform space charge limited current injection into a nano contact solid journal March 2015
Discharge From Hot Cao journal May 1911
Analytical results for the capacitance of a circular plate capacitor journal March 2020
Two-Dimensional Child-Langmuir Law journal November 1996
Analytic Solutions for Space-Charge-Limited Current Density From a Sharp Tip journal December 2021
Current flow and pair creation at low altitude in rotation-powered pulsars’ force-free magnetospheres: space charge limited flow journal December 2012
Effects of emitting surfaces and trapped ions on the sheath physics and current flow in multidimensional plasma systems journal January 2021
Solutions of Laplace's equation with simple boundary conditions, and their applications for capacitors with multiple symmetries journal December 2015
Two-dimensional relativistic space charge limited current flow in the drift space journal April 2014
Space charge limited current for bipolar flow with uniform initial velocity journal June 2021
Approximate analytical solutions for the space-charge-limited current in one-dimensional and two-dimensional cylindrical diodes journal June 2004
Accurate 3-D Capacitance of Parallel Plates From 2-D Analytical Superposition journal February 2013
Space-charge limited thermionic sheaths in magnetized fusion plasmas journal March 2020
A coordinate system invariant formulation for space-charge limited current in vacuum journal July 2019
Two-dimensional space-charge-limited flows in a crossed-field gap journal April 2007
Beyond the Child–Langmuir law: A review of recent results on multidimensional space-charge-limited flow journal May 2002
Two-dimensional electromagnetic Child–Langmuir law of a short-pulse electron flow journal February 2011
Space-Charge Limited Photocurrent journal April 2005
Space charge limited current emission for a sharp tip journal May 2015
A Tutorial on Theoretical and Computational Techniques for Gas Breakdown in Microscale Gaps journal April 2020
Breakdown of a Space Charge Limited Regime of a Sheath in a Weakly Collisional Plasma Bounded by Walls with Secondary Electron Emission journal October 2009
Space-charge limited current in planar and cylindrical crossed-field diodes using variational calculus journal August 2021
Impact of Nonuniform Thermionic Emission on the Transition Behavior Between Temperature-and Space-Charge-Limited Emission journal July 2021
The Capacitance of a Parallel-Plate Capacitor by the Schwartz-Christoffel Transformation journal March 1937
Space-charge limited current with a finite injection velocity revisited journal June 2020