TC Limits

To: tesla-at-pupman-dot-com
Subject: TC Limits
From: "Mark Fergerson" <mfergerson1-at-home-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Wed, 22 Mar 2000 07:29:54 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

  Greetings all, newbie ex-lurker (1 whole week) here!

  Some time ago I posted a request for some TC info on
sci.physics.electromag and was referred here (thanks Dan Kline). I've
been all over the Tesla Ring, and still have some questions.

  A lot of posts about record (large) TC's here of late. Anybody ever
think about record _small_ ones? I'm envisioning a bipolar model;
helical primary 2" long, 4" dia, secondary about 10" long, 2" dia,
running at 1 MHz. It isn't intended for spark generation, but rather
to power a small particle accelerator in pulse mode (I may not even
want a TC; that's why I'm here). The electrodes (rings spaced
exponentially) are the "topload" of around 75pF. I'm looking for about
50KV. I plug the numbers into several TC design programs and I get
reasonable numbers for wire size, number of turns, supply voltage,
etc.

  I picked those proportions from memory of a photo, BTW.

  What are the length/diameter ratio limits for a "good" TC? Why do
some folks think a secondary 2"dx10"l is fine, others say it's less
than ideal? What is ideal, anyway?
I've heard a lot of opinion, but little justification.

  As extreme cases, I can see that a very long secondary would have
too many windings out of the influence of a very short primary to be
worth the trouble to wind, and a secondary the same length as the
primary would would be prone to interwinding arcover, but where's the
breakpoint? What constitutes "long" and "short" here?

  What are the operating frequency limits, and why? I was told a TC
couldn't operate satisfactorily at 1 MHz. Why won't they scale?

  How do you estimate coefficient of coupling for a particular
geometry (preferably without using calculus)? <math pun>

  Anybody think a standard Xenon flashtube (or rather several in
series/parallel) with some kind of magnetic quenching arrangement
would do as a "spark gap" in a low-power design? They're designed to
switch currents quickly at fairly high voltages, their electrodes are
fairly erosion-resistant, and they can be triggered reliably.

TIA

  Mark L. Fergerson