Surface discharge gap

• To: tesla-at-pupman-dot-com
• Subject: Surface discharge gap
• From: Scott Stephens <stephens-at-enteract-dot-com> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
• Date: Wed, 16 Sep 1998 17:43:46 -0600
• Approved: terryf-at-verinet-dot-com

We want a low resistance, fast quenching gap, right? Arcs tend to track or
adhere to the surface of insulators. They also extend farther over them.
This has been used and investigated for switching purposes, resulting in the
so called "Surface Discharge Switch". They have the advantages of rapid turn
on and low jitter, multi-channel (arc path) for low resistance and
inductance, and relativily simple construction.

Dielectrics I've read about include glass, ceramic, alumina and even
plastics like PET (pop bottles/mylar) lexan and best, teflon. Of course
glass, ceramic, alumina would have the best wear character for TC use.

Switches can cool quickly too, in .2 - .5 milliseconds, and could be
integrated into rotary gaps.

G-10 epoxy needssurface conditioning of about 500 shots, during which time
its resitance drops 3 orders magnitude. Alumina 1/4 erosion of rate of G-10,
and after a while the number of arc channels on dropped by 1/4.

Alumina, glass & ceramics rather than erode, get metalized with electrode
material. Aluminal has a E-effective of 10, ceramics and glass around 5.
Some ceramics can (BaTiO:Zr) can have 1000's, but would need to be thick not
to crack under the stress, and would need acoustic (hard rubber) mounting
consideration.

So who has built and tested a Surface Discharge Switch gap? 

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