[TCML] Spark gaps (again)

[jimlux]

Dex Dexter wrote:
> I'm not so sure about thin that much final diameters for a Tesla gap spark.
> Read here (section 3.2) about diameter of steady state and low frequency arc:
> http://www.mintek.co.za/Pyromet/Files/1997Curr.pdf
> I took in my estimate 1000 A primary current arc to expand to about d=10 mm.
> 100 A current is probably closer to low powered coil,but it depends also
> on operating frequency.
> What is radial average velocity of expanding column of such arcs it's hard to tell.
> I don't have data and I'm interested to learn.
> 
> Dex 
> 
> 
Interesting paper.

The diameter data they give is 3cm at 7.8kA.  Also a cathode spot 
current density of 2.4kA/cm2.  At a primary current of 100A, that energy 
density works out to .04 cm2, a radius of about 1mm

If you consider a typical medium sized coil with 130 uH and 0.01 uF 
primary charged with 15kV, the current is about 130A. (based on LI^2=CV^2)


I'll have to track down the paper by Latham, since it apparently talks 
about lightning, which is a fast transient, probably more representative 
of what's going on in a TC primary gap.