Re: coil pictures and observations
Chill the gap. If you like bolts try brass bolts with alternating sizes
of fender washers to act as finned heat sinks. You can also cut nice big
washers out of thin sheet aluminum. A pair of 2" diameter copper pipes 6"
long and at right angles to each other makes a nice gap. The high electric
field uniformity allows them to be put closer together. Large brass balls
make a nice gap but beware that some brass alloys contain lead. Lead vapor
is as dangerous as mercury vapor.
A table of measurements of spark length vs awg would be very
interesting. Different kinds of wire and various tubing sizes could be
tested. Coax has been found to be lossy but I don't recall any tests with
RG214 that has that real nice double weave SILVER plated braid. It would be
interesting to see the result of a primary made with a ribbon cosisting of
parallel silver plated wire wrap wires. I did a test once with a solid
state ESD pulser that used plane ribbon cable for connections. The
waveforms were very nice. The frequency range of operation was several
orders of magnitude above Tesla coil frequencies.