We are using pure tungsten electrodes in a plasma focus device. Thanks to our RG colleagues we removed the oxides from our tungsten electrode, but the oxides came back after our first shot. The source of oxygen was clearly the stainless steel 304 vacuum chamber. We can’t bake the chamber at high temperature as our device requires Mylar insulation which can’t withstand temperature much above 120 C. Running H or H-N plasma at low temperature (70 C) did not work in removing the oxides either. So we are looking to coat the chamber with some material that will not give up oxygen even when (very briefly) exposed to plasma at high temperature. We operate with a N-D mix at a total pressure of around 10 torr.
Refer this link:http://www.instructables.com/id/A-better-vacuum-chamber/
Refer this link:https://en.wikipedia.org/wiki/Materials_for_use_in_vacuum
Refer this link:http://www.vacuumlab.com/articles/vaclab36.pdf
So for the Tokamak TEXTOR in our facility we typically used Diborane (B2H6) to get a better plasma performance and reduce the oxides in the machine (the inner chamber was fully made of Stainless steel. Just the limiter (which stays in direct contact with the plasma) was made from CFC (Carbon Fibre Composite).
As you are aiming for a P,B- Plasma/Fusion this is may be the right choice even so It is Toxic. You could even use it as Fuel.
One Idea that came to me is:
Why don't you try CFC (Carbon Fibre Composite) as an electrode, before you start using Be, Carbon is not Toxic and very stable even under high heat lots and has relative low Z and is of course much cheaper than Beryllium. The main reason it isn't used any more in big Fusion experiment is that it reacts with Tritium, which should be no problem in your case ( as you just use simple deuterium which is not radioactive).
It would be nice if you can do nitriding of your SS chamber wall. For this you need to pump your chamber ~ 10-3 Pa and leak Ar-gas and apply a large –ve bias (~ 600-700 V to the specimen, here chamber wall). Then switch on plasma.
Normally, using nitriding the hydrating is incorporated in vacuum chamber to prevent formation of O.
You can use the "getter" effect of zirconium based alloys. Getters can be used as coating but once applied they continue to adsorb gas and have to be kept under vacuum permanently after activation. Non-evaporable getters are built as devices in various shapes. Since the adsorption effect occurs at temperatures above 150C the "getters" are built with own heating system. Such devices are widely used in vacuum systems including pumps and lamps (like high pressure mercury vapour lamps). For more information, look for "Alvatec Zircon getter" and similar products. These may be easier to use than a coverage of the vacuum chamber. Anyway, take into account the chamber volume, the pumping speed and the getter performance when designing the application.
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