Space Charge Limited Current

Space Charge Limited Current Applet

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        Calculate:   Current      Output Format        Notes

Definition:                           

Equation

Parameters

Diagram

Calculate Current in Cylindrical SC Limited Diode:        top

Parameter

Value

Units

Special Values

Inputs:

 V (voltage)
d (gap length)  
A (cathode area)
         

Outputs:

ISCL(current)

Z (impedance)

 

Output Format:                                                        top

Select Format: Scientific Engineering Fixed

 

Notes:                                                                       top

  • Source:  NRL Plasma Formulary

  • This is for non-relativistic electron emission and transport in vacuum.

  • Assumes no ions (ions generally increase electron current 100% (half impedance), but are a small fraction of total current)

  • Effective area can be spreading of the electron source.

  • According to Bruce Weber (NRL), this equation only works up to about 500kV.  Above this, replace the 2.34 with 2.00 in the coefficient and the 3/2 with 4/3 in the exponent for a better fit.  

 

Copyright © 2002-2021  Raymond J. Allen