RE: Hi Power Discharge "Disruptive"

["Tesla list" <tesla-at-pupman-dot-com>]

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

 >We can't close the loop on coil design until we know how
 >the streamer load behaves and interacts with the resonator.

I should like to think we are getting there in qualitative terms at least. I
now use streamer load modelling in SSTC and OLTC simulations, with an
empirical model based on practical work done by Terry Fritz, Richie Burnett,
and myself.


 >A coil may try to develop say a couple of hundred kV,
 >but breakout will occur as the voltage rises, tending to partially
 >clamp the top volts (we think).

This is indeed what I've seen in lab experiments with the OLTC II. Thanks to
the unique design of this coil, it can produce an output voltage clean and
repeatable enough to be viewed and photographed on a scope, while still
giving enough power for "real world relevant" spark lengths.

In experiments with a 36" streamer at 100 pps, I found that the top voltage
with a breakout point installed was 50-75% of the roughly 600kV it would
have been with no streamer. Thereafter, the streamer load "ate" the energy
in a way that corresponded roughly to the "loaded Q of 6" rule of thumb that
Malcolm Watts proposes. The unloaded Q of this coil is several hundred.

I noticed that the loading is non-linear, being heavier towards the
beginning of the burst, and more or less vanishing once the output rings
down below about 50kV. However the "flywheel effect" of the high Q tank
circuit smooths it somewhat. Also, there was about 30% of variation in the
loading between successive bangs, this probably is due to random changes in
the streamer shape.

It didn't seem to matter much (after the first few cycles) whether a
breakout point was used or the streamer was just allowed to burst out from
the toroid. This is in agreement with the hypothesis that a streamer creates
its own "breakout bump" of plasma, which has the effect of rounding off a
sharp breakout point, or adding a pointy region to a smooth toroid.

The strange corollary of this is that the coil can force a pointy breakout
well above its corona inception voltage, and yet when breaking out from the
smooth toroid, the streamer stays alight even once the toroid voltage has
rung down well below the inception voltage for the toroid's radius of
curvature.

I apologize for not having more quantitative results. The few waveforms that
I have are here:

http://scopeboy-dot-com/tesla/experiment/

Note the "loaded" and "unloaded" results were done with different drive
voltages. I had to reduce the voltage in the "unloaded" condition to prevent
it breaking out from the toroid, so the 50% to 75% is an extrapolation.

Steve C.