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Colorado Demo Fusor

Posted: Sat Aug 12, 2017 10:03 pm
by David Rosignoli
The following are some details of a demo fusor I constructed.
The power supply consists of a negative polarity half rectified NST with a max RMS output of -8.1kV as measured by a voltage divider.
The demo fusor inner and outer grids consists of wire (type unknown since the source has been forgotten, although I originally used stainless steel) spot welded together. My original inner electrode had to be replaced with a smaller one to prevent shorts. Even now the grids appear to be too close.
The aluminum baseplate has a hole upon which the high voltage electrode was JB-weld epoxied (great stuff) on top of a ceramic feedthrough. Another hole was threaded and used for mounting a thermocouple gauge coated with Apiezon wax. The main vacuum port was a KF-25 vacuum fitting JB-weld to the plate.
Using a Welch 1402 vacuum pump I was able to get down to as low as 26microns after a little more than an hour - although it took only minutes to drop down to 57microns from 1 Atm.
The vacuum chamber consists of a pyrex bell jar with a gasket on top of the aluminum baseplate and silicone grease used in between the materials. I am well aware of the ion beam implosion dangers of the setup.
I see a characteristic purple glow so often seen by others. The ion beam is very pronounced.
Thanks,
David Rosignoli
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Re: Colorado Demo Fusor

Posted: Mon Aug 14, 2017 1:04 pm
by Richard Hull
Dave,

Good pump...the 1402 is one of the finest pumps Welch ever made. The pump down time was fast to 57 microns, but the water and vapor load on first runs can be heavy is such a large vessel.
Superb first pass in a demo fusor! Few rack up this kind of win on a first pass presentation. I have added your name to the Plasma club listing.

Richard Hull