Re: Alternate toroid shapes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Dave Leddon <dave-at-leddon-dot-com> 

Back in the sixties I purchased a three foot diameter spun aluminum oblate 
from F. B. Lee (anybody remember his contributions to the Amateur 
Scientist) who claimed that this shape, which resembles a hemisphere on top 
of a toroid, was the best shape for a Van de Graff generator because it 
would accumulate maximum charge while minimizing break down on the 
supporting column.  I often wondered if this shape would represent any sort 
of improvement over the classical toroid.

Dave


At 10:53 AM 12/14/03 -0700, you wrote:
>Original poster: Paul Nicholson <paul-at-abelian.demon.co.uk>
>John Richardson wrote:
>
> > Has anyone done any experimentation into toroid topload shapes
> > other than the typical round designs that all use?
>
>AFAIK little has been done.
>
>Toploads have two important parameters:
>
>a) the amount of charge they hold per unit volt, a.k.a the
>    capacitance.
>b) the voltage at which they begin to issue streamers.
>
>Toroids tend to have a larger capacitance for a given breakout
>voltage, compared with sphere terminals.  And they seem to be
>preferred for streamer formation, perhaps because of this.
>
>But who is to say there isn't a better shape?   It could be
>that the best streamer formation comes from toploads with modest
>breakout threshold plus large charge storage.
>
>You could approximate your proposed tear drop cross section with
>a sphere or toroid with a disc shaped skirt, so that from a
>distance it looks a bit like Saturn.   You would have to tell
>us whether it behaves any differently to a toroid plus breakout
>point.
>
>Plenty to do here for theorist and experimenter.  See recent posts
>by Antonio for the relevant modelling programs.
>--
>Paul Nicholson,
>Manchester, UK
>--