Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
The real aspect to this is that 3MV/m is for a uniform field, and
the fields around a TC are nowhere near uniform. The radius of
curvature of a typical topload is probably in the 5-20 cm range,
which would imply a breakdown voltage in the 150-600 kV
range. Naturally, if your topload isn't nice and smooth (e.g. it's
made of corrugated aluminum ducting), the breakdown voltage will be MUCH lower.
http://www.scopeboy.com/tesla/ol2resonator.html
"The breakout voltage for a 8" x 24" toroid is... something like
600kV"
recently Antonio have posted the chart, and according to it breakout
voltage for this toroid must be equal to 342kv - something wrong here
:-)
8" = 20cm = 10cm radius.. to a first order 30kV/cm so 300kV would be
a good guess.
for what it's worth, trying to calculate breakdown voltages to an
accuracy better than 10% is probably not worth the effort. In
precision sphere gaps, the variability from breakdown to breakdown
with the gap unchanged is in the 5% area.