Reply To: Could pB11 focus fusion device be modified to use thorium?

[Francisl]

I don’t know anything about the leaky valve. At room temperatures tungsten doesn’t react with water so that shouldn’t be a problem. The tungsten blank was formed by sintering and then machining. It had to be frequently heat treated to relieve stresses caused by machining. Sintering causes materials to be slightly porous and the high temperature makes tungsten reactive with oxygen in the air which caused the tungsten oxide.
I don’t know how thick the oxide layer is or how mobile the oxide ions are in tungsten.
According to this report a thin oxide layer should burn off with repeated use. The problem is not going away as quickly as hoped.
Coating the electrodes with a thin layer of silver should reduce or stop the migration of oxide ions to the surface. The only way to know is to try it. If the layer of silver is only a few atoms thick, it should quickly conduct the heat to the tungsten and far less silver should evaporate than if a thick layer is used.
Another advantage of using a silver coating is that it can be used as a base for adding other metals on top of it. Each arm of the cathode could have a different metal coating to see which one or which combination works best.
We have to remember that this is an experiment and problems or mistakes are just another opportunity to learn something new.