RE: water as spark gap dielectric

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Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>



What type of material were they using for electrodes????
They may have been using some type of exotic metal.  I think that during
heavy current arcing, the material
may break down enough to leak material or other oxides into the water thus
ionizing the water and ruining the
spark gap.

The Captain



 > I just ran across an interesting paper by Xiao, et.al.,
 > titled "Recovery of
 > Water Switches" where they look at using DI water as the
 > dielectric in a
 > spark gap (and as the dielectric in a Blumlein pulse generator).  The
 > interesting thing from a TC standpoint is this:
 >
 > 1) DI water has good dielectric properties in short gaps.
 > They reference
 > 1MV/cm, so a TC gap at 20kV would be on the order of 0.5 mm
 > (0.02"). Since
 > gap length is the big factor in gap loss, this might greatly
 > reduce the
 > losses in the spark gap, compared to more conventional air
 > spark gaps, which
 > are 10-20 times bigger.
 >
 > 2) The recovery time for their gap was greatly improved by
 > moderate water
 > flows through the gap. They used flows on the order of 1 m/s,
 > which is not
 > much flow through a tiny gap.
 >
 > Their results showed 1 kHz rep rates at 30kV kinds of levels,
 > and energy
 > deposition into the gap of 1.8Joule/cm for a 0.3mm gap  At
 > 4J/cm, they got
 > 600 Hz reprates.  The typical TC might be somewhat higher
 > energy into the
 > gap, in air, but it's possible that with the much shorter
 > gap, you might get
 > to these kinds of levels.
 >
 > They got best results with an annular gap (where you feed the water in
 > through the middle of the electrode) in a hemisphere against
 > plane kind of
 > gap.  For a TC, maybe something like a piece of copper pipe
 > with a very
 > carefully trimmed end against a flat copper plate with a 20
 > mil gap all the
 > way around. This would give you a lot of area for the spark
 > to distribute
 > the energy around.
 >
 >