From: boris petkovic
Date: Fri, 24 May 2002 09:05:57 -0700 (PDT)
Subject: Re: [TSSP] Topload breakout potentials
Hi Paul,All, (before I return back to mountains) Paul wrote: while the > streamers maintained > the topload at around its breakout voltage (590kV) > then the > total effective capacitance required of topload + > streamers > to hold that energy would be > > Ceff = 2 * E/V^2 = 2 * 16.4 J/ 590kV^2 = 94pF. > > Now the resonator has a Cee of around 40pF so 54pF > must come > from the streamers - 54 streamer-feet at 1pF/foot, > that's > nine at 6 foot. And that loading would detune the > secondary > by 50%. --- I must say that there is (intentionally?) error introduced in analysis above.For start,I offer just a few reasons here to support my standpoint on this matter: Streamer (or streamer-leader if like) loading doesn't detune system that much.With powerfully excited secondary of any properly balanced "input power-secondary size" system you'll get detuning about 10 % the best (Yet coming-up msms are TBD factor there). One cannot attribute all the charge emitted by corona flash (which limits electrode surface E-field tresholds) to be exchanged in post oscillation between top electrode and "hot" arc .Situation is quite difficult to understand (at least was for me ),but corona flash(es)-arc dynamics are multistage nonlinear processes.Seems that nature finds way that great portions of inital flashes termed as "cold" that carry lot of charge "isolate" from corresponding toroid-hot arc current events. If I rememeber,Malcolm send some time ago post "Ion cloud loading" asking for experiment that would decide how much "floating charge cloud" would interfere with shifting secondary frequency down .Experiment shown it turned out very little shift was present? This isn't maybe the best illustration if you have on mind incomparability of these events in energy,peak power violence,and charge perhaps. Question to all:why "end" of power arc from TC shows in many cases much more brilliance than rest of arc channel ?It cannot be only due to possible some higher resistivity or "evaporation" of material particles there I guess.It's diggressing from corona mode discharge discussion but reasons may be related. --- > > Let's see, taking 1pF and 220k per some length of > streamer, > that's a Q of 1/(2 * pi * 66kHz * 1pF * 220k) = 11. > > Pretty low, eh? --- In context what I said already I should say that Terry Fritz linear arc model is "energetic" model of arc.That means it's basically derived from msm of arc dissipation and damping and as such it serves good if you know lenght of arc in advance. ---- > Now that's a worst case because this naive > arithmetic assumes > all the energy passes through the streamers on every > half cycle > which is obviously not the case. --- It's breaking a teeth problem if you think lineary here. Try following "gendanken" experiment.Imagine coil with smooth top electrode.Attach short wire on it and apply considerable power(large bangs) to system.No matter how much you increase power ,top electrode will emit only one arc chanell.Conclusion is that some process must persist that will hold max field bellow certain treshold. --- > > So how're we going to measure topvolts now? We're > stacking > a lot of assumptions onto this 26kV/cm surface field > threshold > but we know that space charge will alter that and > allow the > topvolts to rise further. A scope trace of topvolts > should > match the model to within the accuracy of the firing > voltage > estimate (less a bit for loss) up to the breakout > point, so > that's something we can use to qualify a measurement > method. > Throw in a simultaneous base current measurement and > you can > forget losses and firing voltage - from the Ibase we > can calibrate > the topvolts to around 1% pre-breakout. Therefore > don't worry about > calibrating a topvolts detector if you can provide > the Ibase. > > Those E-field pickup things won't do - they respond > to topload > (+streamer) charge rather than potential, and we > need the > potential. The two are related by the > topload+streamer > capacitance, which of course is varying. The > E-field pickup > doesn't really give any more information than an > Ibase trace, > since Ibase = total external E-field pickup --- E-field probes with a minimum capacitive loading should be placed on surface of toroid.That would help I assume if secondary and toroid are big enough (Thor would serve excellent for performing such msms). Cheers, Boris __________________________________________________ Do You Yahoo!? LAUNCH - Your Yahoo! Music Experience http://launch.yahoo.com
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