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Re: Triggered Spark Gaps - Why Not?
Tesla List wrote:
>
> Original Poster: Michael Veach <veachm-at-sunyit.edu>
>
> Hello.
>
> I read something in this thread which interested me concerning a
> device called a Trigatron. What exactly is it? Does it use Thyratrons or
> ignitrons in place of a gap? I might want to use such a device in a very
> large Tesla system I may build in the future. I hope you can fill in the
> gaps for me. Thanks.
>
> Mike Veach.
Mike,
A Trigatron is a triggered spark gap. It consists of two relatively
heavy electrodes which will ultimately switch the high current power
pulse, and a third insulated triggering electrode which goes through the
center of one of the large electrodes. A rough profile is ASCII art is
drawn below. The gap between the two large electrodes (A and B) is set
so that it won't break down under the applied voltage stress. In some
cases, provision is made from running the device under higher gas
pressures, or with gases other than air.
A high voltage triggering pulse from a relatively high impedance source
is applied to the triggering electrode (C), causing spark breakdown to
its surrounding electrode (A). This is rapidly followed by streamer
formation from the center electrode to the opposite electrode (C to B),
leading to the firing of the main gap. During the initial breakdown of
the main gap, the initial gap current actually flows from the opposite
electrode (B) through the trigger electrode (C) and then to the other
electrode (A), often causing some localized heating/melting of the small
trigger electrode.
In a properly-designed trigatron, the initial high pulse current flow
quickly switches to flowing between A and B so that the center electrode
undergoes minimal damage. Pulse rate is governed by the type of gas and
pressure, and whether the gas is actively purged between firings. By
playing with these parameters, rep rates in excess of 1000 PPS are
possible.
A * * B
* *
* *
C --- *
* *
* *
* *
Hope this helps!
-- Bert --