Enhancing Corona

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

Original poster: "Scott Fulks by way of Terry Fritz <twftesla-at-qwest-dot-net>" <darkthing-at-earthlink-dot-net>

I am interested in doing some experiments on normal-pressure plasmas, and
was thinking of custom-designing a TC to create copious amounts of brush
discharge as opposed to sparks.  Virtually all of the discussion on this
forum seems to equate spark length with efficiency, but I am sure that many
coilers have seen configurations which produce more corona than spark
length.  I'd appreciate any feedback from coilers who have (accidentally or
intentionally) produced a coil that puts out lots of corona.

The way I see it, the secondary frequency is the key parameter for brush
discharges.  If the frequency is high, inductive effects similar to the
well-known "skin effect" come into play more prominently.  The impedance of
a single thick spark is so great at high frequencies that the discharge is
more prone to seek multiple pathways, just as litz wire offers a lower
impedance to RF currents than a solid copper wire.  Multiple small discharge
pathways are seen as a brush discharge, since the human eye cannot resolve
the individual lines of current and just sees a uniform glow.

If this is true, then I would expect the length of sparks from a coil would
be in inverse relation to the frequency of the secondary.  A lower frequency
would give longer sparks.  From the discussions of the importance of large
toploads for spark length on this list, this seems likely.  Large topload =
larger secondary capacitance = lower frequency = longer sparks.

I recall someone on this list awhile back say that small coils seem to
produce more ozone than larger coils.  Is this because smaller coils operate
at higher frequencies (low inductance secondary), or is there some other
reason?

Regards,
Scott Fulks (darkthing-at-earthlink-dot-net)