Re: tesla-d Digest V02 #782

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

Original poster: "Greg Leyh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <lod-at-pacbell-dot-net>


>Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
>
>Hi All,
>
>Tonight I hooked up my fiber-optically coupled current probe to the top of
>the OLTC and made some "small" streamer measurements.  Admittedly, I did
>all this pretty fast and loose ;-))

>[snip]

>http://hot-streamer-dot-com/temp/SFarc02.gif

That's a great shot, as it shows what's really going on
during the growth phase of the streamer -- that the streamer
grows in a rapid succession of small steps, and mostly
during the negative voltage peak.  The train of high
current pulses feeding the base of the arc appear to be
RC-damped, and possibly the result of some relaxation
oscillator mechanism; perhaps with the local capacitance
of the toroid.
Natural lightning strikes also display a 'stepped leader'
mode of operation, as the charges deplete and replenish
around the base of the leader. These natural leaders
have about a 20 to 50uS time constant.

>I look back to Greg's Electrum scope pics of streamers currents at like
>1000X the power:
>
>http://www.lod-dot-org/electrum/sphere05us.jpg
>
>Seems that the streamer is feed by spikes there too.  This suggests that
>streamer currents are many powerful spikes rather than a nice sine wave.
>Or a combination since Greg's and my waveforms have a nice heavy sine
>content along with these spikes too...

Gah, that's an awful photo.  I'll be needing better
diagnostics, like that nice Tek 2-channel digital
scope you have there. <emote>
Seeing those fast, 400nS high current spikes at the
base of the streamer finally convinced me of the need
for a better, RF-grade local reservoir of charge at the
top -- a larger toroid.  The results on the experimental
coil were immediate and dramatic, even though a larger
toroid results in lower voltage.

-GL


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