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Re: Spark Gap Gasses Experiment


Hi Jim,

As a result of this experiment I have begun work on an argon enclosed gap.  

I found that the argon prevents gap fouling.  The copper does sputter off a
bit but the metal tends to return to the electrode surfaces as a clean
copper coating.  With large electrodes and a powerful fan enclosed with the
electrodes, such a gap should be able handle very high power, not foul,
provide excellent quenching, last a very long time, be maintenance free,
and be somewhat adjustable.  

This will be a 25 gap design made from 30 x 6 inch long 3/4 inch copper
pipe sections.  The sections will be in groups of six stacked 5 rows high.
The fan will blow into the sections.  It will have four external taps
allowing for firing voltage of 4, 8, 12, 16 and 20 kV.  I will use plate
glass to make the enclosure in much the same way aquariums are made.  I can
tap the sections with copper strap passing through the glass seams.  I will
have to experiment to find the proper gap spacing for 3/4 inch pipe
sections in argon.  The cost of the argon is very low but it takes a lot of
gas to purge the enclosure of air.  Probably a few dollars worth for 10
cubic feet, (the enclosure is 0.75 ft^3).  I will also have to allow for
gas expansion from heat and weather changes.

The losses my be slightly less than for air.  When one looks closely at the
scope photos, it looks like the loss is less when you account for the lower
firing voltage.  This will need more testing but I looks like it will be
fine.  The large glass surface area should be able to pass the heat to the
outside through conduction to limit how hot the gas gets (~800 in^2 with
1/4 in plate glass).

I would think it would cost a little over $100.  Mostly for the big mean
fan ($75 new).

Any thoughts or suggestions, especially from others who may have tried
this, are very welcome.

I will report the results and construction details when it is complete
(unless it is a flop ;-)).

	Terry Fritz



At 11:43 PM 8/30/98 EDT, you wrote:

>From: Jim Monte <JDM95003-at-UCONNVM.UCONN.EDU>
>
SNIP>>
>
>  I would tend to agree that the freon experiment wasn't that useful
>  due to the toxicity, but the argon results could be useful if the
>  gap is opened up so the firing voltage is the same as in air.  If the
>  losses in the primary and the quench are the same or better, it may
>  be reasonable to shield the gap with argon.  This would eliminate
>  gap fouling.  I recall paying about $50 for 249 cubic feet, so the
>  gas is not that expensive if bought in moderate volume.  With the
>  reduce maintenance that an inert gas would allow, enclosing the
>  spark gap and filling the enclosure with argon would be another
>  possibility.
>
>  Jim Monte
>