Re: desirability of high coupling...Re: primary INSIDE of secondary?

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

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

A

> > 2) There is a huge effect on spark growth and shape from the RF envelope,
> > and the coupling (and relative tuning) of pri and secondary.  It's possible
> > that you don't want too fast a rise of the RF energy in the secondary, to
> > give the sparks time to develop and lengthen?  Consider that a Marx bank
> > with a single impulse is sort of a similar thing to a very highly coupled
> > TC (i.e. all the power is there at the first RF cycle)... Marx banks
> > generate sparks that look very different from a TC.  (Has anyone built and
> > tested a 120 pps reprate Marx with a couple hundred kV output?  At first
> > glance, one might expect the output to look like a TC)
>
>I imagine that a Marx bank, or any other DC HV generator, would not
>produce streamers, that require RF current in the channels started
>as corona. Arcs with complete terminal discharge look almost the same
>for any generator.

Bazelyan and Raizer mention streamers forming from very high voltage DC 
sources (>1MV) and being a enduring phenomena:
" Quite different is the corona behavior in a gap with large electrodes. As 
the voltage rises, the continuously glowing envelope breaks up into 
separate patches, in which longer filaments, fancifully shaped channels of 
cold light, appear and disappear again within a few microseconds.....  A 
streamer corona produced in a large air gap at voltages above 1 MV looks 
like fireworks. A streamer may be as long as several meters; numerous 
bright streamer channels cross the dark space of the laboratory room with 
such a noise that the experimenter can not hear his own voice.  The pulse 
current of a propagating stremer only lasts for a few fractions of a 
microsecond and is measured in amperes, even in tens of amperes. ... If the 
laboratory voltage source permits, a streamer corona an be observed lasting 
for many hours.  It does not lead to short circuiting, because, for this, 
it is necessary that the streamer channels cross the whole gap space, which 
normally occurs in atmospheric air at an average field of about 5 kv/cm."

One of B&R's more poetic passages.. clearly they are impressed by the 
appearance, and these are guys who make 100m+ discharges at many MV and many MJ



> > 3) Part of the coupling thing is the relative resonant frequencies of the
> > primary and secondary (leading to "beats" (aka "notches"))...again, this
> > affects the RF envelope, which probably affects the spark "look".  There's
> > also a change in the resonant frequency of the secondary as the spark
> > develops...
>
>The effects of the envelope on streamer development are still
>mysterious,
>I think. The detuning when the streamers develop may be not a so serious
>problem if the coupling is high. And even with low coupling, the system
>may "tune itself" to a certain average streamer length.


The more this gets discussed, the more I think about figuring out how to 
make a numerical model of the entire system, including the spark channel..



>Antonio Carlos M. de Queiroz