It came to my attention I'd neglected to put a link here to my microwave ion source, which I'd documented on the old web page. So here it is.
This is one of the larger successes around here -- it's performed like a champ for 100's of hours without a glitch, till the wire to the puller extraction electrode came loose inside the tank, which will be easy to fix the next time I have to door open. I don't yet know how well it will work with run-of-the-dumpster microwave oven tubes, because the first one I tried worked great, and no reason to mess with it further, as in, this one works, and no one has offered to pay me to make them one. I used the lowest power tube in the junk pile, which seems like it was a good idea.
ECR (electron cyclotron resonance) ion sources have some cool features. No metal electrodes in the "nasty zone" so no sputtering. Since it really is an electron cyclotron, once it's started you can take it ridiculously low in pressure and it will stay lit. Even at crazy long "mean free paths" for the gas present, the electrons just keep going round and round till they hit something and ionize it. Where nearly all other ion sources make mostly diatomic ions (in this case D2+), this one makes predominately monatomic ones. And mine at least will run down to the e-5 millibar range easily, once lit at somewhat higher pressures.
For what it's worth, after a long good fusor run, we sometimes see neutrons coming from the ion source with everything else turned off. And you can turn them on and off with the source power -- perhaps some of the fusion byproducts (T and 3He) are easy enough to fuse for that to happen. All I know is, it happens and only after a long fusor run when the various byproducts have built up. I can also see them on my mass spectrometer, as I pump the system back down through the pressure range it will work in.
The nice thing about the 2.45 ghz frequency is the magnetic field needed to get to resonance is big, but not too big. In other words, other stray fields (like the earth's) don't mess it up, but you can still easily generate the field needed with good NeFeB magnets you can get fairly cheaply. For lower frequencies, the cavity gets a little too big to be practical, and the stray field issue is larger.
We recently acquired some ~8 ghz klystrons I may try this with too, but they are pretty low power devices (fraction of a watt) and may not do for this. If so, we may use them for plasma diagnostics instead.