Space Charge Limited Emission

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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

bullet
bulletSource:  NRL Plasma Formulary
  • This is for non-relativistic electron emission and transport in vacuum.
  • Assumes no initial electron velocity.
  • 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  Raymond J. Allen