From: boris petkovic
Date: Wed, 23 May 2001 11:50:10 -0700 (PDT)
Subject: Re: [TSSP] Genetic optimisation
Hi Paul,All, > Looks like 26kV/cm is the figure to work with at > normal TC frequencies, > - comes as some relief that the value is not > severely frequency > dependent, things would be tricky if so! --- Surely,~26-28KV/cm critical surface field would be all right to assume for TC freqs (and standard atm.conditions) Definitely,if such field appears for a certain time ,it will get show to start happening per see. But,what counts the most here is one thing:TIME... By this I don't mean just time of TC waveform exceeding this treshold ,but also time pauses between 2 primary condensers bangs-->in other words some depedence on BPS (belive it or not!). John Freau experiments with smooth toroids are very valuable when we speak of this matter. He has noticed smaller bang size (innital cap energy) needed for visual spark breakout with higher BPS rate than with lower BPS rate. Few months ago,I contacted with M.Denicolai and he said he would make controled experiments on his thor in order to investigate such phenomenon this summer . Something else you should know as well.With about 400 KV peak voltage on his coil Marco was unable to get breakout of his 20*150 cm smooth toroid. Only with Ep~10 J he started to observe first faint streamers coming from the terminal. Question improved E-Tesla program should answer to: What max. toroid surface field corresponds to 400 KV voltage on THOR secondary? ---- > > If I've understood things right, the leader > formation begins and > continues as long as this gradient can be maintained > just ahead of the > leader. I guess the significant threshold involves > meeting this value at > the surface of the smooth toroid and once a leader > begins to form, its > sharp point will then ensure that the leader forms > rapidly for quite > some distance - even though the 'background' field > from the > topload would, by itself, fall below the 26kV/cm > threshold only a little > way from the surface. Subject to the toroid having > enough charge > available to support that formation. What stops the > leader formation? > I guess either it hits earth or it runs out of > charge - the toroid is > depleted and the 26kV/cm cannot be maintained at the > tip? So a big > toroid would be reluctant to break out (modest > surface gradient), but > it would throw a long streamer as soon as it did > (lots of charge > available)? > > I'm afraid I've got some more questions! > > > A long spark (>6 cm) is characterized by multiple > avalanches in an > > evolutionary sequence: streamer flash(es) --> > leader propagation > > (fed by groups of streamers) --> spark (if leader > > bridges the gap). > > Can we assume that this whole sequence takes place > in a timescale short > compared with an RF cycle - I suppose thats so > because if not there > would be a bigger frequency dependence? --- I think we can,althought some scopings on 250 Khz+ coils I saw in past ,displayed not so small differences. --- > > When the HT falls away, do things recombine and > settle down sufficiently > that on the next half cycle there is no 'memory' of > the previous half > cycle? > > Ultimately what I'm fishing around for is some > confidence that some > acceptable and realistic account can be taken of the > breakout > thresholds, otherwise attempts at non-linear time > domain modeling will > founder on that point. I feel as though we are on > top of the technical > matter of computing the response and now, quite > suddenly it seems, we > are up against this more difficult problem of > finding a load conductance > function which provides an acceptable summary > description of the > breakout dynamics. > > If I've got things right, then Terry should be able > to calculate quite > easily the top voltage at which streamers should > suddenly start to form, > and we might also be able to calculate an estimate > of streamer length > too (as a function of topvolts). Given those two > separate figures (or > functions) we would then have the choice of > optimising for max topvolts > or max streamer length, using the same genetic > software but with two > different merit functions. > > Cheers, > -- > Paul Nicholson, > Manchester, UK. > -- Regards, boris __________________________________________________ Do You Yahoo!? Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.