Fusor Forums

Late last year, maybe in October or so, I got around to building a very quick and dirty demo fusor with some junk and spare parts lying around the lab I work at over a couple of lunch breaks. I originally found a small stainless vacuum chamber that was thrown away in the university tech docks trash maybe a year before, and finally got around to putting it to use since I didn't have a vacuum pump for myself at the time. I added a simple acrylic viewport on the bottom that was bolted between the bottom flange and a metal adapter using a rubber gasket I punched out of some spare rubber sheet, which worked perfectly fine for the low vacuum I was achieving. The demo fusor uses two simple spiral grids made from copper wire, filled with just plain residual air for the plasma gas. It is powered with a variac controlled, current-limited, full-wave rectified MOT for simplicity. I pumped the chamber down with a Welch Duo Seal 1400 pump. There was no instrumentation or vacuum gauges to check the pressure, so I do not know what vacuum it reached, but it was sufficient for a nicely stable and confined plasmoid with very little effort. The first wire I used for the inner grid rapidly overheated due to it being made of copper and having been far too thin, nearly melting after about 10 seconds of running. I swapped it out with a very thick heavier gauge wire which still glowed red hot during operation but lasted much longer. I managed to get a couple of good pictures of the plasmoid during operation.

Here you can see the first grid assembly with the thin wire before it overheated, operating in jet mode:
Here is the second thicker grid during pump-down before a good vacuum was attained for a plasmoid to confine:
Here is the second thicker grid with the fully confined plasmoid, also operating in jet mode:
This demo fusor was just for fun and to see if I could do it with the scraps lying around. While it was not intended for anything more than a fun side project, I do plan on eventually designing and building a fully fusion capable fusor for the new student nuclear classroom at the lab as a learning and teaching tool (obviously not with this setup.)

Nice system on the cheap. Looks like you are between 100-50 microns on the bugle jet. I have added you to the Plasma club.

Richard Hull

Thanks for the add! I forgot that there was a plasma club in addition to a neutron club. Even though it is pretty trivial compared to a fully neutron producing system, it is really encouraging to push forward with more advanced experiments, and hopefully I will have the chance to join the neutron club one day. You really have a lot of experience and insight to gauge the level of vacuum from just the pictures alone too - it's definitely very helpful to have an idea of the range it was operating at.

As noted in the fusioneer's preamble, the plasma club is an expression that such a person within it has got up off their behind and actually done something to a limited degree towards the fusion effort!!

We find about 95%, or more, of those who make the plasma club, never do fusion for a whole host of reasons.

Richard Hull