From: "Terrell W. Fritz"
Date: Fri, 25 May 2001 13:40:10 -0600
Subject: Re: [TSSP] Genetic optimisation
Hi Paul, Bert's 26kV/cm number is very good. When the voltage on a sphere of 1cm radius reaches 26kV it will arc outward. It is a linear function so a 2cm radius sphere is 52kV and a three is 78kV... Us high altitude folks have a bit differnt numbers due to the thin air up here ;-)) My spark gap distance are differnt than most poples since I live at 5400 feet. The chart at: http://hot-streamer.com/TeslaCoils/Misc/SGapVolt.jpg "may" be useful here... A toroid's surface is a bit different than a sphere and has the toroid diameter as an additional factor. E-Tesla6 can do this calculation for a given case but does not provide a simple equation. However there is probably one for this or it can be derived. I suspect the answer is very close to 26kV per cm of cord diameter. Cheers, Terry At 05:45 PM 5/23/2001 +0100, you wrote: >Hi Bert, All, > >Bert Hickman wrote: > >> I only wish I had more time to devote... > >I wish you had too - things always seem a lot clearer after you've put >them into words. > >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! > >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? > >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. >--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.