Science/Engineering/Technical forums

Alright, we've been EXTREMELY busy since my last post, so this is going to be a long one. Our radiation shielding team decided to orient he reactor vertically now versus the previous horizontal arrangement. So we had to re-run all of our fill and vacuum lines after we had them fixed. Its their part of the project and it looks so much better now, so I'm okay with that. So our new setup is shown below. To put the reactor in that new cage structure, we had to take apart the hemispheres. This was the first time it had been open since we got our first plasma back on March 1st. We found that the 304 Stainless Steel was now a golden color on this inside. From my research, I have only been able to find that 304 SS turns "gold" at 400 C, orange at 500 C, and so on and so forth. I don't really have a better explanation than that, does anyone else? So after we got the reactor reoriented, we held a fusion test on April 27th. This test was...interesting. First I'll start off by saying that our He-3 detector has been malfunctioning lately. We replaced the cable between it and the amplifier and apparently that messed it up. So for the last two tests we've run, we really don't know the counts we got. However, we had two other neutron detectors to let us know if we were generating any neutrons. Our highest reading during the April 27th test was 0.6 mr/hr, so we got something. The first video below, to me, shows what we have been looking for visually. We finally got it to "transition" from that star mode to a point where very little light was coming from the center of the cathode. The current was constant throughout the course of that video.
The second video...around 8 seconds I got zapped when the power supply was at 23 kV. Somehow, the multimeter we were using to monitor the shell temperature of the reactor got put RIGHT next to the HV feedthrough connector (but it's housed in some conduit). So my guess is that it was putting out a field that the multimeter didn't like (because it was going crazy), so when I reached to turn off the multimeter, it arced from that connector to my ring (large class ring). Lesson learned on that one...I am fine and it wasn't too bad of a zap.


Ok, so after that test, we were finally able to start conditioning with Argon. The main difference besides that is the fact that we put in a 3 loop, 0.032 inch diameter Tungsten whisk (1.6" diameter) that looks more symmetrical to me. When we ran the test, we got up to -32 kV before we got an arc (all time high for us at the moment), but our He-3 detector still wasn't working. So our reading for this test was consistently above 0.5 mr/hr, but spiked to 1.23 mr/hr and up to 0.9 mr/hr pretty often. So from this, we're estimating that we got about 100k neutrons, but its pure conjecture. At the moment, we're working to fix the He-3 detector and put in some 5% boron by weight borated poly we got for neutron shielding (we're going to monitor any gammas that come out of that). Hopefully we get a test in this week, but I'm graduating Saturday, so this may be my last chance to run it. I'll pass on this info to next year's team, so hopefully they get "better" results and put them up on here.

Yes, definitely looking lots better -- both in pure looks, and it how it seems to be working now.

You guys deserve kudos for going from nothing to something pretty good in a short time and with low resources. Now that kinda defines a good engineer!
Hopefully we won't lose all of you -- are you all graduating this year?

He3 tubes are notorious for cable problems, the least speck of dirt on the insulators (or the wrong wire type in the cable)....they tend to run real high voltage and with a weak signal, it doesn't take much to mess them up. I and many others have gone to building the preamp so it goes right on the tube to avoid some of that.

We had terrible troubles with getting zapped too, and the reasons may not be obvious. First of all, there's no perfect insulator, so in the absence of something to take charge off the outside, it eventually builds up to full voltage -- and can store some energy due to its capacity to ground, usually in the 10's of picofarads at least - enough to give you a good zap.

Also, since there's no ground there -- everything else acts like the other plate of a capacitor to this. So it all gets a charge, which was what was getting us here. The human body can get pretty far off ground while on sneakers, and the next ground you touch -- bam.

We fixed all that by putting metal screen on the outside of all our conduit, grounded. Works great, and will surely show you if there's any bad spots or pinholes in your insulator to boot.

Good show people!

I apologize for this late posting, but yes, we are all graduating. Luckily I know someone on the team for the August 2011-May 2012 team, so I will make sure (hopefully) he gets on here and posts some milestones. Also, the other team leader from my year is now a grad student and he has told me he has followed this thread. Hopefully, he makes some posts of his own if he does some work on the fusor this summer. It pains me to say that I left the fusor the way it was. We had a leak in our vacuum bypass loop that I could have fixed, but we were able to run without it so it was put off until it was too late. The shielding folks got the 5 wt% borated poly shielding up around the fusor (6 inch blocks all the way around). I'm sure the plan is to monitor the radiation that shouldn't come out of it once a new fusion run is done. As for me, I'll check in on this thread from time to time, hoping to stay up to date on how this baby runs. I GREATLY appreciate all of the aid and encouragement we have gotten for our fusor; it would have been much more painful without it. Thanks especially to Doug; the visit we made to view his working fusor and the tips we received were invaluable. Maybe one of these days once I get to a more stable point I'll build a nice setup of my own, but that's years down the line.

Go Hokies .

Well, from us all -- best of luck on your post-graduation life, it really starts now. I think that at least you just got a good object lesson on the difference between apparently simple and actually easy to do -- this one won't be the first, so buckle up and kick butt out there! I didn't meet anyone in the group I don't think can do real well.

We'll of course welcome the next batch of y'all and try to take this to the next level. Here we are just doing this despite any particular life cycles, onward and upward.

Go Hokies indeed