From: Paul
Date: Tue, 15 Oct 2002 08:52:32 +0100
Subject: Re: [TSSP] Top Voltage
Boris wrote: > I find useful to repeat them one more time Terry wrote: > Forgive if I am to blame for any of that. Don't worry about it. There's so much stuff crossing this list at the moment that it's hard to keep up, especially when things are two steps forward and one backwards all the time. I have the same problem at this end, absorbed in code and formula it's hard to see the overall picture sometimes. Often, important comments don't get picked up on, so the poster must keep on plugging to get things through. > I think I will put foil on the ceiling Could be worthwhile. I'd say it'll reduce your breakout threshold by at most 20%, but that would bring it into ballpark with the value predicted from Boris's formula. Boris, have you anything more on the conditions under which the empirical formula for the sphere's Emin was obtained? Are we on the right lines by taking 30kV/cm as the threshold for a uniform field only, and expecting the non-uniform (sharp drop-off away from the surface) to raise the threshold quite a bit? I suppose that if the tinfoil ceiling was made adjustable in height, it could be brought down closer to the raised sphere, so that the breakout would approach tabulated sphere-plane discharge conditions. We could measure breakout volts against different positions of the 'ceilingplane' and compare those with calculated field non-uniformity. We hypothesise that the more uniform situations (smaller sphere-plane distance) will approach the 30kV/cm. The system of toroid, rod, sphere, and ceiling plane lends itself very well to field calculations. Everything is smooth, no sharp edges, so field calcs should be trustworthy. I'm working up a program to plot the fields. Lets hope we can correlate some sort of average gradient with the measured breakout surface field. -- Paul Nicholson, --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.