Colorado Demo Fusor

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David Rosignoli
Posts: 146
Joined: Thu Mar 04, 2004 2:57 pm
Real name: David Rosignoli

Colorado Demo Fusor

Post by David Rosignoli » Sat Aug 12, 2017 10:03 pm

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.
David Rosignoli
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Richard Hull
Posts: 12290
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Colorado Demo Fusor

Post by Richard Hull » Mon Aug 14, 2017 1:04 pm


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
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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