Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: thermionic cathode
Date: Nov 08, 11:21 am
Poster: Jim Lux

On Nov 08, 11:21 am, Jim Lux wrote:

>>why not insulate the inner electrode.
>>ie. cvd coat the inner electrode with silicon dioxide or aluminum oxide.
>>the inner electrode will capacitively couple and the insulating layer will lower the electrodes emmission.
>No one has tried that here yet. Someone should. Remember the same number of electrons will hit the inner grid as before and the same heat will be there. Some oxides work better as emitters than the bare metals. Some investigation would be needed.

Probably some sort of tungsten carbide is what you want... you want very high thermal emissivity (so you can radiate the heat away at relatively low temps).

Actually, the best strategy would be something like is used in power grid tubes (which the fusor, basically, is) and put a suppressor grid in front of the inner grid to deflect the electrons away. The real problem is the mechanical tolerances necessary.

Study that Eimac handbook...