A new fusor build!

[Doug Coulter]

No real hard data yet -- I'm still building up the instrumentation for fusor #2, but an interesting observation anyway. I had done the build with the new super accurate composite carbon/ceramic grid, and it was fairly punk and acted kind of strange -- just as that grid did in the big tank -- I obviously have some learning to do on that one. So, I put in an old standby grid, one that's been reliably the second best here in the other system, so as to just get the new one kind of working at a baseline. It acted funny too -- in about the same way.

This led to me noticing that it was a little off center, so I adjusted that via the nice ability that feedthrough design gives me to do things like this -- about 1/4" or so. And now it acts a lot less "funny" -- a LOT.

Due to that screen electrode I have based about 1/4" off the bottom of the tank, at least when it's grounded, I don't have a perfectly round applied E field anyway, and the grid was also off in the direction of being too close to the bottom. This makes me want to fiddle the bias on that, which I've not done yet. I grounded it because it burned out a perfectly good 1k resistor and was arcing over the LV feedthrough I had it connected to....so some experiments suggest themselves. It goes negative (no surprise) when left to float, something over -8kv (which is out of scale for where it is, interesting -- I'd expect more like 1/12 of the HV)....lots of electrons flying that way. So to bias it (assuming a little bit negative would tend to restore the field shape to normal) all it would take is some series R to ground for the DC side of things. Since I'd been doing those interesting field perturbation experiments on the other system, with promising results, that's why I put that in there in the first place, to do that better. Well, evidently grounding it perturbs the field "better" indeed and that wasn't a dumb idea if followed all the way through. We'll see soon enough. I want a localized neutron detector rather than the ones downstairs, which will now be complimented with the gamma spectrometer -- this smaller unit might be better for that testing I want to do on reaction pathways, and do it at a lower level where I'm not catching so many rems, always nice.

At any rate, a small amount of grid position change took it from a diffuse glow, to having "rays" again, and more stability at the running conditions. On the axis of where that screen electrode is -- still no rays...so this seems like it's explainable, and even controllable, and that the grid centering is a lot more important than previously mentioned (here or elsewhere). Other observations there have shown me that a slight twist in the grid rods is also a big deal. This seems to be telling me that our "emergent behavior" that gives the good neutron output is a fairly sensitive function of the initial "simple" conditions -- a butterfly fart can throw things a long distance in such conditions.