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Re: [TCML] Voltage Question
I'm sorry that my mailing program somehow screwed my formatting up
in my last post, making it almost unreadable.
I wrote:
> An important parameter seem time scales to me.
Paul Nicholson answered:
The streamers advance in steps which are probably quite rapid
compared with an RF cycle. Hence the topload has to supply
the sudden amounts of extra charge and that is why I suggest
the topload C matters for arc length. It is functioning as
a reservoir which banks the slowly arriving charge from the
coil and makes it available at low impedance for streamer
extensions.
Ok. My emphasis was more on longer time scales. It seems, that
it takes a certain amount of time to get enough energy into an arc
to make it long and hot, probably much longer than an RF cycle.
This is not explicit in an relation between arc length and power only.
I wrote:
a) Resonant frequency periods. These are probably too short to matter(?)
On further thought this is untenable. David Sharpe posted a reference
http://www.dtic.mil/dtic/tr/fulltext/u2/a526052.pdf
which contains some interesting measurements. I find the pages
7-21ff of particular interest. The authors describe there the power
consumption of RF corona of a 1 inch wire. They observe a steep rise
from corona onset (113 kV) to 1 foot flares (124 kV).
In their semi-empirical formulas the power consumption
is proportional to the RF frequency. The idea is, that the power
is dissipated in the region between the wire and the outer edge
of the corona by the flow of charge in between. The location of
the outer edge is given through the condition that the field there
is equal to the breakout strength. (Pages 7-7ff)
Paul Nicholson wrote:
Given a sufficient supply of charge, the streamer should
extend until its tip field strength drops below about 26kV/cm...
This suggestion is much along the the above mentioned line.
I want to emphasize the role the frequency plays. The streamer generates
a cloud of charge creating a current which stops at the time the cloud
has built up a field countering the terminal field. After polarity change
that charge is sucked in and a cloud of opposite charge is created.
The average current is proportional to the frequency. If there is not
enough current, there won't be enough energy dissipated in the streamer
for it to grow.
Paul Nicholson wrote:
I suggest a point would be reached where increases of top
voltage, topload C, or envelope time, would not extend the
streamers any further (for any given toroid minor diameter).
You lost me here. Why is that?
Udo
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