Definition: Richardson-Dushman Equation

The Richardson-Dushman equation relates the current density of a thermionic emission to the work function (W) and temperature (T) of the emitting material:

j_s = A T² exp(-W/kT)

where

j_s is the current density of the emission (mA/mm²)
A is Richardson's constant (approx. 1202 mA/mm²K²).
T is temperature (K)
W is the work function of the cathode material (J)
k is the Boltzmann constant (1.38066E-23 J/K)

In Cathode Emissions in CPO, A is treated as an empirical constant. In fact, j_s may be entered directly.