I decided a couple weeks ago that the best approach to building a neutron-generating reactor is to first build a kind of scale model, known in the amateur world as a “demo” reactor. It is basically an air plasma reactor that doesn’t actually produce fusion but does require high voltage and dealing with a vacuum chamber. Since I have little experience with HV and no experience with vacuum chambers, I need to get up to speed on the nuances of both. Basically, this first model has all the features of a fusion reactor but doesn’t require as much skill, kind of like learning to walk before trying to run.
I spent many hours at the hardware store last week seeking out parts and then many more hours experimenting in the garage to come up with construction methods. The photo above is the inner grid. This is the reactor core where, in theory, the fusion takes place. The shape is important, it should be spherical or at least cylindrical. It is made of four loops of stainless steel wire held together with a wire crimp. The other end will be crimped to my high voltage feedthrough.
And what is a high voltage feedthrough and why do you need it? The reactor works by applying a very high voltage between two electrodes. The inner grid is the negative side. In my design, the positive side is the metal vacuum chamber wall. The negative voltage must get through the wall without shorting out, it does this by going through an insulated feedthrough. The feedthrough must also be vacuum tight.
Seems like a tall order, but this is exactly what a spark plug does. It feeds a high voltage through the metal car engine casing into the cylinder, and it forms an air-tight seal. So I bought a spark plug. Unfortunately, the electrode on most plugs does not protrude enough to attach my grid with a wire crimp, so I bought an oil burner igniter plug, shown at right. These can easily be found on the internet and cost only a little more than a common spark plug.
You can see by the photo that the electrodes are much longer. However, the thread size is exactly the same as most spark plugs.
Like everything in this project, it can’t be used right out of the box without modification. The ground electrode must be cut off and actually the central electrode is too long for my design, so I had to cut a bit off as well, pictured on left.
My current plan is to make my reactor fairly small, mainly because buying a large vacuum chamber is amazingly expensive but also because I want it to fit in my garage for now. So the objective for this first chamber is to be approximately the same size, that way I can get experience dealing with smaller dimensions. For instance, the grid at the top is less than an inch in diameter, which will be the size of the grid in my neutron generating reactor. It ain’t easy dealing with such small structures…
In other news, all kinds of vacuum parts have arrived. Unfortunately I am still waiting for parts for the vacuum pump. In the meantime, I was able to test out my stand-alone gauge connected to what will be my backing pump isolation valve, pic below (reading atmospheric pressure)…
Next: The chamber being constructed, made from a common object. Can you guess what?