Beam-target neutron generator project

[Doug Coulter]

Carl, I like that HV FT design a lot, just forget to put that in my earlier post.

As maybe "the" magnetron ion source guy I have some comments that may help you.

I would not do this at 60 hz pulse rate. That's just enough time between pulses for the "light to go out" and the ionization mechanism have to "re-strike" on each pulse. In work here, I've found that this re-striking will only work over a narrower (and higher) pressure and power range than is needed for CW, and that 60hz is just on the slow side. Even a few khz is enough faster to avoid that problem here.

Even then I get the thing "lit" at fairly high pressures (about what a fusor likes) where it's easy, then it will stay that way all the way down to e-6 mbar levels and below, where nothing I can find will light it off initially, including a huge DC bias or "magnetron power set to 11" (DC also used to extract the ions so it's there anyway in mine). It's fairly painful to have to let in gas to re-light the thing if it goes out, so in my case anyway, it's best to avoid it going out!

I would bet, but haven't tried this, that those inverter type microwaves would do a fine job - there will still be a few ions and electrons loose when the next pulse comes around to avoid the issues with re-striking from scratch. Could be the ECR magnets I have in there help to keep a few around longer, dunno.

You may or may not want to fool with the ECR magnets I used in my design, or reconfigure what I did. I have the magnetic vector pointing along the ion tube, which kind of creates a pinch at the outlet, making them somewhat harder to push out. Things might work just as well with the magnets turned 90 degrees (across the tube) but still orthogonal to the RF field (across the tube vertically in my design). The reason I like having the magnets is that it gives you another octave or two lower pressure over which the thing operates well -- and here you might be working in just that range where it's marginal without them to get good mean free path for good beam focus control.

I'm not sure I'd worry about a "mere" 40uA just yet. If the book numbers are true, that's going to be a lot of neutrons - probably a record for here - when this is working the way you want. I like to walk before running myself.. "Fantastic" can precede "stupendous" and it doesn't bother me, anyway. More current is going to bring up heating issues anyway...

Here's the link to our blather about uWave ion sources -- there are now a few of these out there built and working great. http://www.coultersmithing.com/forums/v ... f=28&t=222

[Larry Upjohn]

Carl;
MuggyWeld struck a gray cell back there and I think I may have asked this question previously. The website and the videos also struck a bell. I will post my results when completed. I had just purchased some 360 brass rod to redo the flange and avoid the Al to Brass bonding issue, however I have several other aluminum flanges and the Al soldering issue is just around the corner anyway. Thanks again, Larry Upjohn.