RSG electrode material

From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Wednesday, April 08, 1998 7:11 PM
To:  Tesla List
Subject:  Re: RSG electrode material

Tesla List wrote:
> ----------
> From:  R M Craven [SMTP:craven-at-globalnet.co.uk]
> Sent:  Wednesday, April 08, 1998 12:59 PM
> To:  Tesla List
> Subject:  RSG electrode material
> I am still trying to compile as much info on RSG electrode material as
> possible.
> The reason why is this: building an RSG is expensive, so I want to
> make the best choice on metal for electrodes. Pure or thoriated
> tungsten is costly, at least it is in the UK. The same goes for
> tungsten carbide forms if they are in the right shape (1/8" by 1" rods
> etc.), and other material such as Mo is almost as costly.
> I've had good info off Malcolm (as usual), and Durlin Cox and Bill
> Wysock. Who else can contribute information to help me out?
> Check out this site:
> http://web.iquest-dot-net/cmw/
> I think Elkonite is a suitable material: low ablation rates, high
> temp. working, easily machined using tungsten carbide tools. Pulse
> Generators, I think, refers to Elkonite. The point is that the W/Cu
> alloys will form protective oxides which further lowers ablative
> damage. Craggs and Meek, Glasoe and Lebacqz, Sargeant and Dollinger
> all refer to significantly improved gap life when run in an
> oxygen-containing atmosphere.
> Thanks in anticipation
> Richard Craven, Malvern, England.


I agree with your assessment. However, I also checked out the prices or
Elkonite (and similar powder metallurgy Cu-W alloys) a while back - this
material's considerably more expensive than plain pure tungsten rod. The
major advantage of this material over tungsten is it's improved
electrical conductivity which makes it very useful for spot-welding
electrodes. It is also claimed that copper-tungsten alloys give the
longest life (minimal electrode erosion) in triggered high current spark
gaps (in a nitrogen atmosphere - Vitkovitsky in "High Power Switching").
However, tungsten comes in at a close 2nd place. From a practical
standpoint, tungsten seems to be the most cost-effective choice.

BTW, a couple of other references that cover sparkgap electrode
performance and erosion can be found in:

A.L. Donaldson, M.O. Hagler, M. Kristiansen, G. Jackson, and L.
Hatfield, "Electrode Erosion in a High Energy Spark Gap", in the Digest
of Technical Papers of the Fourth Pulsed Power Conference, 1983, IEEE
cat 83CH1908-3, pp530-533.

However, the best overall modern "bible" on high energy sparkgaps is:
Gerhard Schaefer, M. Kristiansen, A. Guenther, "Gas Discharge Closing
Switches", Plenum Press, 1990, ISBN 0-306-43619-1. Look for this book...
it's definately worth getting!

Hope this helps...

-- Bert --