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: New tantalum grid - fusor III
Date: Jan 07, 12:24 pm
Poster: Richard Hull

On Jan 07, 12:24 pm, Richard Hull wrote:

I placed my newly fabricated grid in Fusor III last night and did early tests. The new grid took about 3 hours to fashion. It is made of 9998 pure tantalum wire, .110" in diameter. This is about 4 times the diameter of the original grid which has survived for over a year. The new grid has only spot or reisitance welded joints. The old grid was silver soldered. Still, it held up better than expected.

The old grid wire diameter, upon inspection, had suffered a naturally sputtered reduction to nearly .015" in places! Also, the old grid did not melt!! It just fell appart. (two loops) My guess is the silver solder probably sputtered away at a key joint until the excess heat softened it enough to overcome the small remaining surface tension.

The new grid was outgassed and the chamber glow cleaned for one hour prior to test. I counted 15 star rays with the new five ring geodesic with the pressure in air down to submicron levels. (TC gauge bottomed out below zero peg.)

This new grid is not nearly as pretty to the eye as the old one, but seems to function as good or even better, especially in the power handling area. I beefed up key joints with .002 tungsten tire wrapping and silver solder reflow backfilling. The old grid came apart at just over 400 watts. The new grid just starts glowing at this power level. So, I am looking forward to fusing perhaps this weekend with it at yet higher levels.

Richard Hull