Cowboy data aq on some ion dynamics with fusor as ion trap

[Doug Coulter]

Just a placeholder to get a URL for discussion on some videos I'm waiting to to upload.
More when that's done.
Here's the first one, just the basic setup stuff.
https://youtu.be/_vO0KHkm-Rk

This shows I'm using an old but great GR bridge oscillator signal generator that has real oompf - and is still accurate after all these years - to drive the bottom of the L in a series tuned circuit, with an arbitrary L that just felt about right, driving the capacity of the fusor feed-through and grid. Gets to some decent HV! (no load here)

The second one where I jerry-rig a temporary repair so I can get data.
https://youtu.be/pHOJ04cpcm0


The third one might take till tomorrow, as it's big, and I'll be asking the smart guys here to chime in on interpretation.
The numbers are "interesting".
It'll be here when it gets here: https://youtu.be/DKfnZM0VTlM


Now about that roughly 48 ns delay we see, and the evident bunching (sort of). Any smart guys have an idea/explanation?
All I have are guesses...

[Doug Coulter]

EDIT: Don't get faked out by auto-scaled plots - even I missed it at first, and I've had practice (see, stock market ripoffs that make little stuff look dramatic).

A little more info. I lashed up the MiniVNAPro in place of the GR oscillator, added a 2.5mh choke to ground to protect it from stray junk...and made a run around the resonance with gas, but no ions present (yet). The choke dropped the resonance around 1 khz, so I'm glad I checked with it in place - I have no idea about any tolerance for DC or transients in this thing, so..I did what I could (and it did live, no upper arms were bruised).

Here's the stuff as jpg and as pdf (which is where I got the jpeg - the jpeg export function in the VNA doesn't get the marker data)

No ions. Gas is present around 2e-2 mbar of D indicated.

VNA_180623_144740.pdf

PDF version, no ions

(122.08 KiB) Downloaded 217 times

Now with ions - I ran the ion generator grid out in the main tank with the current limited small spellman. Same everything else (And I didn't measure the dc volts there, frankly it's lit or not lit and not much matters other than that - it's a sensitive function of gas pressure1 - we'll get there but it's going to take more data aq gear work).

With ions, same other parameters

VNA_180623_144625.pdf

PDF with ions

(131.33 KiB) Downloaded 224 times

1. The above looked slightly odd to me, so I went and ran it all again...I *didn't* hit the same gas pressure on the nose (it's hard) and had a little more, about 2.2e-2mbar indicated. And it made a huge difference with ions present - but none without them. With just this much more gas...the resonance and Q are lowered a LOT more. FWIW, running fusor in DC mode, the run above at 1.9-2e=2 mbar is where we get best Q - or really, the lower the pressure we can run the better it seems to get, but you run into a hard limit if you can't get it to light off, hench all this work on ion sources and so on. It seems here that we have a fairly major bit of new evidence that just this little change - +10% or so, makes ALL the difference!
HMMM....implies a few more ions are producing more effective capacitance and some resistance here. FWIW, I ran the little scope while it was scanning with the same vertical scales, and the VNA signal just didn't show up at all...milliwatt vs watts from the GR I suspect.

Ions, higher pressure

VNA_180623_152853.pdf

pdf of same

(102.18 KiB) Downloaded 226 times

That VNA just paid for itself, I might not have noticed this without it. And I may get a better one that lets me insert some power amp into the loop and still get the same type of measurements - this seems to be a very much NOT scale-invariant kind of thing, which is kinda how I thought it would be.

Edit: using the calculator here with the measured inductance of the coil I get 28.9 pf effective without ions, and 29.1 with the most ions above. So 0.2 pf effect.
Which, being due to kinetic motion will likely change with both frequency and drive level.