- The setup. Main grid in the sidearm, ion grid just visible at lower right.
FWIW, the neutron detector we log is a hornyak, totally shielded with internal preamp (coax to counter at 5v levels) positioned about 1" in from the end of the sidearm at the lower right, eg, much closer to the main grid than the ion grid. Assuming inverse square law, it should count lower for a given neutron production in the ion grid, since it's a lot further away...but we see what we see (also in X rays, from a separate sensor, behind lead and lead glass, with loud output (have to attenuate the 40v pulse at the counter/logger) and it correlates with the neutron counter (capture gammas?). At any rate, the only thing with power applied was the ion source. Since our plasmas are net-negative, it shows some main power on that graph, but that's just because the main grid is acting as a faraday probe (else the later Q plots would show infinite Q for this part, since we don't log the ion power at this point - we will later on). So that loud neutron and X ray output that ends around 100 seconds is "all ion grid" if you can believe that - I'm going to have to deliberately replicate it and see some signals on a scope free of EMI, as this is "too good to be true" - but you never know.
- ?anomalous output 50-100 seconds The pi cam above was taken at the same instant as the screenshot - 700-something seconds into the run
Ah, but we're really here to see the pi cam in action. It took a 2.5 diopter lens from reading glasses (we old farts know about this one) to get focus, could use a little more, but I've lost my higher power ones for the moment. At any rate, today's mission was to get a couple decent pix with the pi cam and with the cam in the shield, which I managed to do, so let's look at one. This is earlier in the main-power run, before things heated up in there very much.
- Here's what she looks like - pretty close to the mark 1 eyeball, but I'm not getting fried anymore.
After things heated up some - we generally show a somewhat reduced neutron output after some running as the D is driven out of the stainless steel fusor tank walls (that's our guess why, anyway - charge-exchange and beam on target fusion at the tank wall when it has D in it). So, here it is, hot:
- I need the color temp to be right for the hot part, or I might melt something...so this is important for remote running.
As usual, you can click the pix to get a larger version, though I did scale it down from 2500-something to 1280 horizontal rez to save space. At this low light, it doesn't really lose much of anything but wasted internet bits. The sparkles in these are because though I have an extra lens and an extra near-ir filter, the pi camera still gets hit with X rays (inside a lead box to keep them out of the room). Kind of a nice backup if you know what you're looking at/for.
Of course, I am logging things while we do this, as in the screen shot above. Here's the full log plotting vs time. After the run, I put the silver on the geiger (pancake) counter, it's a foil the same size as the sensor. You can see where it took me awhile to think about doing that and get it done - we see some background at my normal levels while I'm making the move.
- Post-run, with silver decay once I got it to the geiger counter
On the screenshots - this is very raw data, unprocesed as can be. The plot window marked A/D Inputs has blue as pressure (already log compressed by the pk251 sensor), purple is a 2.49v reference diode we calibrate the rest against (later), red is the main HV voltage, green current. I started at 9.8 current limit on the big guy, but went up to about 15 ma later, as you can see from that plot (and the neutron output). While it doesn't show on this plot, there was a small negative voltage picked up by the main grid near the 0-200 second range, or the later Q plots I'm going to show would have blown up mathematically. The initial low volts that you can see on this were because the pressure was far too high for either the current limit or any real neutron output (you can see the main HV was pretty low before I got the deuterium pressure down).
And now for some data mining...since I set a limit on this board of N pictures/post, I'll do that as a reply to this one. I wrote a perl program to drive gnuplot from our log files, and it can do all kinds of pretty neat things, like use that 2.49v reference we log to really know what the a/d full scale range was - super important since we have to re-exponentiate the pressure sensor output, and it can do math, like compute the Q (or really, anything you want to type in), point by point....nice tool, if you understand its limits. For example, we get neutron counts even when nothing but the detector is on - cosmic rays. Nope, no infinite Q, we know darn well those are not good data....we still show them because we know what we're looking at.
