The Breakdown in a Low Pressure Glow discharge is
well known phenomena. It's general form follow:
Because of changing density and
mean-free-path of electrons in a glow discharge cell, Breakdown voltage is variable.
And the minimum of the paschen’s curve is the effective position for
maintaining discharge. (it's just pressure-dependant factor. The Diameter of a cathode
is fixed)
It's named as "Paschen's Curve". And ,
Numerical Expression follow:
Where Ai and Bi
in the expression are empirical values, and ri
in the expression is secondary ionization coefficient for the target metal.
Empirical factors are
added. As the Results, We can know that VBD
is depend on the pressure and diameters(or distance) of glow
discharge cell.
Some Scientists use this phenomenon as discharge diagnostic
method.