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2nd demo fusor run

Posted: Wed Aug 23, 2017 5:05 pm
by Filippo_Passeri
Hello, everyone.

This is my second fusor run, and I think it would be good to share the details. The biggest problem is the vacuum. From the plasma, I can estimate that the pressure is around one torr. That is not surprising since I only have an unidentified lent vacuum pump from school. Because of the high pressure, the current in the vacuum chamber exceeded my measurement capabilities (above 200ma). Since the pressure was so high, the inner grid was very inclined to short through the ground plate and fool the vacuum even more. Because of the shorting tendencies of my inner grid, I tried to isolate it, but that proved to be worthless since the plasma got through the isolation nonetheless.

So currently the highest thing on my to do list is to get or find a better vacuum pump. The second highest item on my list is to fix the wheels on my fusor since I completely underestimated the weight of it (see pics).
Here you can see the voltage meter (top) and the scaled out current meter (bottom).
Top view of the grid.
My inner grid plasma.
Here you can see the destroyed insulator on my feedthrough (spark plug).
The destroyed wheel bearings on my fusor mount. Need to get bigger wheels.

Re: 2nd demo fusor run

Posted: Thu Aug 24, 2017 2:00 am
by ian_krase
I think that's much worse than a torr, and you maybe have more issues with leaks than pumps.

Re: 2nd demo fusor run

Posted: Thu Aug 24, 2017 10:52 am
by Dennis P Brown
I do not see a gasket for the bell jar to base seal? One really needs to use a gasket if one expects to prevent massive leakage - vacuum grease alone isn't going to work very well. This may be causing the high pressure in the bell jar. Also, this is a safety issue since glass on metal can create dangerous stress points.

Also, you should consider making a better high voltage feed through than a spark plug. Placing a copper rod with a light coating of a good grade of epoxy through a thick wall ceramic tube isn't difficult and allows more versatility in electrode attachment as well as a providing an easy place to drill/thread a screw for the high voltage external wiring.