Re: TSG Construction

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

>
> Has anyone used a piece of sheet metal with a hole in it (say 1-1.5
inches -
> maybe a large washer) with the edge of the hole filed very sharp (like a
> knife edge) as the trigger electrode?  This is placed perpendicular to the
> main gap electrodes so that the main arc goes through the center of the
> trigger electrode hole.  Supposedly Maxwell Corp discovered the sharp edge
> greatly increases the field intensity and causes multiple channel arcs in
> the main channel, lowering the gap resistance and thus the losses.  Seems
> worth a try.

This sort of trigger electrode is fairly common in commerical units.  Big
rail gap switches (imagine a pair of big parallel massive rails) often use
an adjacent smallish wire as the trigger, although in recent years, laser
triggering has become more common, since you can control the jitter more
easily.

>
> Terry I noticed you did a variant of this with a wire loop as a trigger
> electrode.  How does that work as compared to the typical setup with the
> trigger electrode being similar to the main electrodes but perpendicular
to
> them?

The "rod poking in from the side" is probably not a particuarly good
approach.  One thing you generally want is symmetry in the gap: gives good
consistency, fairly uniform fields (that get perturbed on the trigger pulse,
but not before), no hot spots, etc.

Looking over some of the literature, it looks like there are only a few
popular configurations (partly for mechanical reasons, I suspect):

1) Three ball gap (swinging cascade) with three basically identical
spherical electrodes. Trigger applied to middle ball, which is biased at
Vgap/2

2) Trigatron (concentric trigger electrode within one of the main
electrodes): very popular configuration, with various forms of triggering
(polarities relative to the two main electrodes)

3) Knife edge between spherical (or hemispherical) electrodes

4) Multi gap with a stack of disks separated by some insulating spacer.
Trigger applied to multiple disks within the stack

5) various rail gaps, with half cylindrical (or Rogowski profile) parallel
electrodes and a trigger wire next to one of the electrodes (noticably
closer).

There are some weird ones used in big lasers, too.. one where the main
electrode was metal screening (shaped like a Rogowski) with an array of
small points behind it.  The trigger created a discharge between the points
and the screen, which "drifted" or "illuminated" (it's not clear which) into
the main gap which was the laser cavity.

t>
> --Steve
>
>
>
>
>
>
>