# RE: SSTC does 10 foot sparks- statistics

```Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com>

>Coil A puts out 10 foot arcs with only 1kW RMS power measured at the plug.
>Coil B puts out 5 foot arcs with the same 1kW RMS power measured at the
>plug.

This post of Dan's was a good example of what I was saying about spark
length obeying statistical laws. If Coil B strikes 5ft once a minute, then I
know, and I'm sure most of you will agree, it's not going to produce a freak
spark that beats Coil A's 10ft, even if I run it non-stop for six months.

In other words, the whole gamut of spark types, from 120 hits-a-second
"controlled spark", to the freak "holy cow did you see that", seem to happen
over a fairly narrow range of toroid-to-target distances. So for instance if
I place a target 5ft away from my big OLTC, it will just be a solid power
arc, but at 6ft, it will hit it maybe once or twice a minute.

However, my experience is with OLTCs, SSTCs, and DC spark-gap coils, which
have a very constant and predictable bang energy. With an ASRG or static gap
system, things get more chaotic, and I expect the distance between solid
power arcing and occasional hits will get greater.

I haven't done the experiment, but my gut feeling is that if we plotted the
frequency of hits vs. the toroid-to-target distance, all suitably
normalised, we would get an energy distribution like the Fermi-Dirac
distribution

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/disfd.html#c3

except with distance as the variable rather than energy. The "temperature"
in the F-D equation would be a constant that described the randomness of
streamer growth in general, and the randomness of bang energies in your
coil.

If this was the case, then the most logical way of rating your coil would be
by quoting a "Fermi Distance" and a temperature 8-P

Or we could just forget about it and go blow some more IGBTs...

Steve C.

```