Well, it kinda worked on the first try. Not super -- there are issues, but it does work, and it does detect neutrons and not other stuff.
Here's the lashup. I pretty much used what the data sheet Joe found suggested. 5 ten meg resistors in series. 210 pf coupling cap, 10k load R to the scope probe.
The "issue" is that today, as sometimes happens, the nearby weather radar (normally a boon around here -- nice to have one in your backyard to get accurate pix from it) is really hammering us, and making every possible ground loop ring. That noise on both sides of the real pulse is there with the scope probe shorted to itself, not connected to anything else, and you can actually watch the big dish swing -- it comes and goes periodically. This will obviously require a preamp to get to TTL kinds of levels and low impedance to be reliable in the presence of things like that (like I've done for the other neutron tubes and counters/scintillators). I'll probably get better pictures later -- that radar doesn't normally bother things this badly, but it's a weird weather day, so maybe we're seeing extra reflections or beaming from that.
So here's a typical pulse. I could have cleaned it up a bit more with scope settings (heck, it was in 1 ghz sampling peak detect mode which gets *everything* no matter how slow the sweep), but till I get rid of the radar interference, no point really. I got pulses from about 1 div up to about 150 mv or so, various backside ringing, nothing all that hard to deal with compared to any other detector. If we didn't know it ran in the mysterious corona mode, you'd never notice. The normal overshoot after the pulse due to cap charging, nothing special -- looked better than in that paper Carl found.
The thing is, it's not real sensitive at all. The B10 tube below it on the same rack was going 100hz or more while this was doing 1-2 hz counts (lousy eyeball estimates of course), and the 3He tube was cranking at hundreds of HZ on the same neutron output. On the good side - it has next to zero background, undetectable right now till I clean up that other noise. Note that this isn't way off scale from the estimate you'd make based on the comparison of tube volumes and surface areas -- the other B10 tube is enormous, and so is the 3He. There might be another 2-3x if we can pick off the marginal pulses from reactions oblique to the tube walls with a lower trigger threshold.
It's already a cubic crap-ton more sensitive than a BTI, and realtime -- bonus.
The datasheet says "1400-1600v" for this. I tried 1400, it worked, I tried 1500, it works better -- and now I'm up here typing. More to come, perhaps, since the fusor is ready to go with a single button press right now. But it really looks like I need a nice, tightly shielded loud output analog preamp before doing much more with this. Should be a matter of two transistors more or less, probably off a 9v battery, as that will all fit inside a little box I can mount on there tight, and give nicely big pulses out that will make this noise not an issue at all. I'll see if I can design one for this signal that won't run batteries down fast -- I'll shoot for 1 ma.
Looks like a qualified winner -- I'll see if I can get it better. If we can kill off that RF noise (which isn't this thing, as I said, the scope shows it with shorted probe just being on, and not even connected to system ground to pick up ground loop noise) maybe we can set a decently low threshold and pick up more sensitivity. It does count even when the big fusor is very much underperforming -- it would work fine for someone just starting out.
FWIW, I happened to have a spark plug wire connector sitting on my end table that fits the nub on the tube perfectly, so that's what I used for this. A type plate cap ought to fit too. I grounded the detector tube with a bit of spare flashing I shoved down in the hole with it for a tight fit.
Interestingly, even with the very sloppy looking lashup, even when I had arcs on the main HV very little of that got into the scope signal...that last modification to clean up any radiation from that at the source really works nicely.
And oh, there's those other two tube types to test now that I have the lashup basically going...