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Re: Any info available on Vacuum Gaps?

On Fri, 30 Oct 1998, Tesla List wrote:

> Original Poster: Richard Hull <rhull-at-richmond.infi-dot-net> 
> 
> >         Not to quibble, but please explain the breakdown mechanism in the
> gaps
> > which "quency well".  I believe that the pressure in commercial vacuum
 > > capacitors is more nearly 1E-6 than 1E-9, so don't see how your gap
(as
> > contrasted to a vacuum relay) could work in the same sense as a gap in
> > air.
> >
> > Ed
> 
> Ed,
> 
> A vac gap is not the same as either a vacuum switch or a vacuum capacitor
> All are
> designed for different purposes.   A true manufactured vacuum gap is
> designed for
> ultra rapid quench and extremely infrequent operation.  TR switches are
vacuum
> gaps, but are made for continuous operation at low average power
> disappation. (not
> what I am taking about.)  Vacuum arc break down (protection) gaps are
> designed to
> indeed work in the 10E9mm range.  Most are trigger type gaps design for pico
> second quenching.  Most all rely on field emission for avalanche or
> radioactive
> deposition the arc lasts until the original high energy source is removed
> by any
> number of mechanisms. (usually related to additional sensor circuitry or
> discharge
> of the firing capacitor)  Krytrons and Sprytrons (EG&G) are a good example.
> 
> I am unaware of any vacuum gaps having ever been made for continuous high
> average
> power arcing operation.  This is why it would be wise to discourage any
> attempt at
> casual construction which would be virtually impossible.  Especially at
> very high
> average powers.
> 
> A vacuum switch relies also on extremely infrequent service and a vacuum
> capacitor
> relies on never approaching breakdown (hopefully by careful design).  They
> function well at 3 orders of magnitude higher pressures.
> 
> Richard Hull
> 
> 
> 
> 
The Bell Electric Spark gap tube 1B42 had the following ratings:

 Repetition rate min:160pps
		 max:1500pps	
Peak current:300 A (yes A for Amps!)
Pulse duration 6.1 uS
Max operation voltage 17.4KV
Min operation voltage 10.5KV

 This rating sheet goes on to say that radar Spark gap tubes had been
designed to handle 25Kw - 2.2Mw, and even some experimental designs that
handle 15Mw.

With these numbers from 1949 why would it be impossible to build your own
high power Vacuum spark gap?

Ben Bouxsein





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