Re: water as spark gap dielectric

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

Original poster: "colin.heath4 by way of Terry Fritz <teslalist-at-qwest-dot-net>" <colin.heath4-at-ntlworld-dot-com>

hi there,
             i really hope this will work but will hydrogen be a problem from
arcing in the water
cheers
colin

----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, April 17, 2003 6:12 PM
Subject: RE: water as spark gap dielectric


 > Original poster: "Lau, Gary by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<Gary.Lau-at-hp-dot-com>
 >
 > Intriguing, but my understanding of using DI water as a dielectric is that
 > the duration of the pulse must be brief, or else the water will break
 > down.  In a TC gap, the gap voltage ramps from zero to the breakdown value
 > at a lazy 60 Hz rate.  Does my understanding require revision?  I hope so,
 > this sounds like a great way to improve gap efficiency!
 >
 > Gary Lau
 > MA, USA
 >
 > --------------------------------------------------------------------------
----------------------------------------
 >
 >
 > Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > <jimlux-at-earthlink-dot-net>
 >
 > 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.
 >
 >
 >