I wrote:
Paul Nicholson wrote:> There'll be a voltage drop along the arc and at some point... it seems a bit extreme. I can't imagine an endlessly growing streamer given infinte power but just a certain voltage.
the arc will reach sufficient length for the tip not to have a local field strength high enough to make further extension.
You're probably right. I was thinking along that line and my first ideawas, that spark channels had a much too low resistance to causea voltage drop. On the other hand the currents in the streamermight be in the ampere region so the voltage drop might well benear your guess.Do you have parameters of Jacobs ladders at hand? This seems alsoa case of low voltage and long arcs.An important parameter seem time scales to me. I can think of these:a) Resonant frequency periods. These are probably too short to matter(?)b) Voltage decay times in sgtcs or burst lengths in drsstcs.c) BPS times.d) Ion or heat lifetimes (may be very different).There was a discussion in this list in May last year about QCW sparks,where long arcs were reported from low voltages. Since say 100 BPSsgtcs don't show this effect, the interesting times seem to liebetween b) and c). d) might just be in that region, but I don'tknow. Likely the speed of streamer growth also dependson the voltage or charge on the top terminal.Paul Nicholson wrote:>...the calculated breakout voltage (derived fromArc voltage drop would depend on streamer current which in turn depends on operating frequency, duty cycle, etc. How much, I don't know but maybe in the range 100V/cm to 1kV/cm. For example a coil might break out at 200kV and need another 25kV to support a 50cm arc. These are just guesses.
toroid radius of curvature and using 26kV/cm as the breakdownfield strength for air at TC frequencies)Do you know an easy way to calculate the field strength fromvoltage having toroids? I'd just guess for V/r using the smallerof its two radii of curvature. I'd be thankful for a ballpark estimate.Udo
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