Oops, a calculation for anode length is under design parameters in wikipedia. Although they still don’t mention how the insulation length is figured.

http://en.wikipedia.org/wiki/Dense_plasma_focus

From some of the articles I’ve been reading it seems that it’s kinda of a trial and error process. I’ve attached an article that states this, it’s on page 1816.

“Unfortunately, there are still not
validated theoretical models to determine the dimensions of
the insulator. Therefore, several tests with different insulator
length and diameter, scanning pressure range from 1 to
12 mbar, were necessary to determine the size of the insulator
in order to obtain a homogeneous initial sheath.”

This article was not through the university, it can be found through google, but I’ve attached it anyway. If it doesn’t let me attach, the name of the article is

“Research on Pinch Plasma Focus Devices of Hundred
of Kilojoules to Tens of Joules”

Brazilian Journal of Physics,
ISSN (Printed Version): 0103-9733