Semi lame walk up and run a fusor video

Tales of woe that teach. We learn best through failure sometimes
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This is for tales of woe that teach. We often learn quickest through failure that shows us how our thinking was off, and of course, sometimes it's funny at least in hindsight. Share your "Doh!" moments here.

Semi lame walk up and run a fusor video

Postby Doug Coulter » Sun May 08, 2011 4:46 pm

Nothing like John's recent contribution, but then I had to also hold the camera after perhaps too many beers. Shows how stable this is now -- it'd actually been set up for a couple hours (so I could drink the beer and find a working camera) -- all I had to do was walk up to it and hit the HV on button. A little better look at that radar noise vs real neutrons on the scope -- sometimes it just takes a movie to get it across.
and of course inline:

The main HV shut off because I was pushing it a little too hard at the end there -- it's fine, and puts out a goodly bit more than the spec (which is 40ma, not the 50 I pushed it to).

A full run takes more effort. First, you turn the turbos to standby and block off the forepumps so that little valve between them can control gas outflow. Wait for the turbo to spin down (I help that along with a shot of D inlet), then balance the gas pressure, here between 1.9 and 2.2 e-2 mbar indicated. You're ready at that point, and the power supply voltage and current tell you much more about whether you have the right amount of gas in there than anything else (except peering in the window perhaps). So a few tweaks during a run, usually doesn't take much with a clean system that is neither outgassing or losing gas to cleanup.

This shows the cheapo Russian mini B10 tube working great, despite some noise from the local weather radar -- looking at the lashup, a little noise shouldn't be a surprise. I'll soon test the other Russian tubes (a bigger B10 and two 3He's, also bigger) but this bodes well for beginners -- these are plenty good enough to get someone started, and the price is, well, not like we whine about from the official sources of these kinds of things. It's funny that some of the others in our community demand that you have a super sensitive (and expensive and hard to find) 3He tube, when these things work just dandy. And for those of us who have working fusors -- the super duper stuff is swamped with the resulting neutrons, and the cheaper stuff actually works better. We're not trying to tell the difference between none and a few -- we're after power generation -- huge numbers, heat!

I can't easily hear the difference between a few kHz count rate and some tens of kHz after all - it all sounds like shhhhhhckckck. And at super high count rates, you counter may be missing things due to pulse pileup and not even be monotonic -- pileups can caused missed counts at the higher rates, so just shoving the signal into a digital counter isn't a panacea at all -- it can lead you seriously astray. Thresholds can be good -- but like FM radio -- can also throw away information. But you can sure hear the difference between a few and a lot down in the lower ranges. For example, when my fusor is cranking (much harder than in this movie) -- it is very hard to tell which channel is counting faster right up at the speakers, even though it's maybe 10::1, once both are fast. In the movie, I was running about 1/10 of our normal best numbers, this was just for show and giggles.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
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Location: Floyd county, VA, USA

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