magnetic insulation and aspect ratio

• To: tesla-at-pupman-dot-com
• Subject: magnetic insulation and aspect ratio
• From: Eddie Burwell <eburwell-at-HIWAAY-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Tue, 21 Dec 1999 17:25:21 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

  I've been mulling over the issues of designing a secondary coil and have
looked  at a number of factors that come into play. First I noticed that the
maximum L for a given length of wire occurs at a H/D aspect ratio of .46.
Then I noticed that the minimum self C occurs at an aspect ratio around 3.
Now I'm wondering about the effects of magnetic insulation i.e. the magnetic
field of the resonator will deter charged particles from traveling
perpendicular to the axis of the coil by deflecting them tangentially around
the coil. This effect would be most significant inside of the secondary and
at the exterior surface of the coil. Now the tricky part is that peak
voltage on the secondary occurs at the same time as zero current and peak
current occurs at the point of zero voltage. This would mean that the field
would not effect streamer formation (if it occurred at peak voltage) but
could influence the lingering arc channel. 
  If the effects of magnetic insulation play a significant role then a
longer aspect ratio may be preferred so that the inductance of the secondary
is reduced and the resonant current in the secondary is increased. Perhaps
conductive shunt plates at the ends of the coil could also be used to
squeeze the magnetic field around the secondary to some benefit (as well as
lowering the L).


Any thoughts?

Eddie Burwell

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