Good information Joe. Thanks. I figured that the ionizing current, fil-to-ionizer grid, might need to be a bit higher than the main device current. I had no idea that the voltage needed to be so high though. I figured that around 300-500 volts we would maxout. Oh, well.
The filaments will not be as efficient as when in the 5U4 tubes originally, but should do OK at our low draw. They could easily support over 500ma of electron current in the high vacuum tube they were originally placed in. I figured an order of magnitude reduction would be acceptable for our work in the medium vacuum level we use and allowing for a heavy lossw in value of the oxide coating after being exposed to the air.
By the way, another question.........Could you see the filaments optically with your eye? What color were they while pulling 3.5 amps? I would not run them over bright orange to the eye. Finally, you may have to flash them or carry them up to a very high temp for a few seconds under vacuum to help prep them for use each time the system is dismantled. To do this, you may want to not apply the 30kv accelerating potential but concentrate on the fil-ionizer grid voltage alone. Just some thoughts on things I would try if I was getting your results and wanted to explore other possibilities.
You are the only one with "something on the stove" right now and it is a new area for anyone on this list as relates to fusion or fusor operation. Needless to say the "handling dynamics" of this new arrangement is a must master sort of thing.
I realize, and can appreciate the fact that you have to go home to experiment. This means you can't just test at will, but with the herculean task of moving my setup and completing fusor IV, you may beat me to the tasks above even at spring break! Thanks again for answering my questions.
Richard Hull
Created on Friday, January 19, 2001 9:34 AM EDT by Richard Hull