First Reactor Test

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Jeremy Adams
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First Reactor Test

Post by Jeremy Adams » Sat Jan 03, 2015 9:13 pm

I'd like to share a picture from my reactors first test. I've been working on this model with a friend for a little while now. Although our model doesn't compare with other reactors it was still an accomplishment considering that we are sophomores in high school. We plan to run our reactor to get our plasma distributed equally which will occur when our deuterium is shipped in a couple days (in the picture it's ionized air with the positive output grounded to the top of our chamber).

We used a neon sign transformer (NST) for our high voltage source and built a full wave rectifier to separate the positive and negative charges from the NST's AC output. Our output voltage was 8.1kv (the peak of the AC sine wave) but we didn't use a capacitor to smooth out the voltage fluctuation. Our negative pressure vacuum almost reached 10^-4 torr and our chamber had leaks but held for the few minutes of our test.
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Adam Szendrey
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Re: First Reactor Test

Post by Adam Szendrey » Sat Jan 03, 2015 9:45 pm

Going well so far. When using a glass vacuum chamber it's best to surround the cathode with an anode grid (an outer grid connected to ground works just fine). With your cylindrical chamber you could just put a wire helix (a few turns) in there going from end to end on the inside of the glass wall (given that the endplates are metal, though I can't tell from the photo, as despite the fact that there are metal bolts holding together the two endplates there doesn't seem to be an electrical connection between them suggesting they are made of something non conductive...?). Otherwise your field distribution will be very asymmetrical. I'm guessing you are planning on doing that. Are you sure the pressure was in the 1e-4 range? Looks higher to me.

Deuterium (gas) is a big investment at this demo stage. In my opinion it's better to first get a decent chamber, vacuum system, and HV supply together and test with air. Admitting deuterium in your system would most probably be a waste (unless you have very sensitive neutron detection equipment). You can read up on neutron production ,and suitable HV supplies in the FAQ sections.

Jeremy Adams
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Re: First Reactor Test

Post by Jeremy Adams » Sun Jan 04, 2015 1:35 am

The plates on my chamber are aluminum and thanks for the suggestion on linking the positive charge to both plates. The metal bolts probably have impurities which cause less of a formal electrical connection. Also with the mention of deuterium I agree that it'd be more suitable to use with a better reactor chamber, HV source, and vacuum. I probably won't inject any into this model as I know that fusion doesn't occur consistently until the 20kv range. I'm planning for a welded steel chamber and greater power supply in my next reactor model- which is when I'll actually test for fusion.

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Rich Feldman
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Re: First Reactor Test

Post by Rich Feldman » Sun Jan 04, 2015 2:19 am

Looks promising there, Jeremy.

As Adam said, the plasma appearance is not consistent with an absolute pressure of +1 x 10^-4 torr. 10^-4 bar I might believe. What kind of vacuum gauge are you using, and how is it connected to the chamber? Learn why pump specifications are not a useful indicator of chamber pressure.

As you said, lower pressure should make the glow cover all of the grid wire. You need a shorter, larger diameter vacuum hose and/or a less leaky chamber. I bet your pump performance is not the problem. At this level, a quick way to find leaks is to brush some vacuum pump oil on the outside of each seal, while the pump is running. Pay attention to changes in the pump sound or the glow appearance, as the oil temporarily plugs the leak.

Then you could turn off the electricity, wipe off the outside oil, and look for signs of inside oil.
All models are wrong; some models are useful. -- George Box

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Liam David
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Re: First Reactor Test

Post by Liam David » Sun Jan 04, 2015 2:29 am

With that plasma, you're not below 75-50 microns. Better plasma is generally achieved by a lower pressure, and "star mode" occurs at below 15 microns. What type of pump are you using, and do you have a vacuum gauge?
Also, you said that you full wave rectified the NST. Since NSTs are center tapped transformers, the case will float at about half the transformer's rated voltage if you use a full wave rectifier! Here for more info: http://fusor.net/board/viewtopic.php?f=29&t=4405. Just like Adam said, the FAQs are a great place to start.
Where did you purchase the deuterium and how did you get them to sell it to you?
Off to a good start!
-Liam David

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Chris Bradley
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Re: First Reactor Test

Post by Chris Bradley » Sun Jan 04, 2015 12:30 pm

Jeremy, your chamber is running at around 1~10 torr. You need to improve the vacuum by 4 orders of magnitude to create 'fusor' conditions, and preferably by 5 or 6 before you admit deuterium, if that is your end objective.

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Rich Feldman
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Re: First Reactor Test

Post by Rich Feldman » Sun Jan 04, 2015 5:36 pm

Thanks for the calibrated eye, Chris. I bet yours is the most accurate of three recent guesses here.

By way of encouragement, Jeremy,
I bet you can get one or two orders of magnitude improvement today.

Find your leaks and figure out how to make them go away.
Plasma appearance is a good enough vacuum gauge at this point.
The lessons learned will serve you well as you move forward.
-Rich
All models are wrong; some models are useful. -- George Box

Jeremy Adams
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Re: First Reactor Test

Post by Jeremy Adams » Sun Jan 04, 2015 5:58 pm

My previous calculation for negative pressure was probably wrong and I attached a picture of my pressure gauge during a vacuum test we did earlier. It gets about -90kPa. It's attached to my chamber with a barbed hose fitting and braided tube. Would it be a good investment to get a better vacuum system if I resell my current pump on ebay or should I improve other aspects of my fusor first?
Here's a link for my NST (it's the 3rd model Me-120-9000-30): http://neonpro.hyrite.com/docc/Product-Me-120.htm
I read the FAQ but I'm not sure I understand correctly but I attached a circuit diagram just to clarify how I rectified the AC current (but I didn't use the capacitor to smooth the current).
The deuterium I'm getting from Cambridge Isotopes Labs (CIL) is 25mL and its getting shipped to my friends family's company (whose also working with me on the reactor). To get it shipped we had to have it sent to a company (not a residential address) and briefly explain our use for it. I think it was a good choice to order it earlier than latter because we ordered the smallest quantity (and therefore they may not ship it as soon).
Thanks for the advice guys
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Liam David
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Re: First Reactor Test

Post by Liam David » Sun Jan 04, 2015 8:34 pm

Oh, that's why. You're using a "modern" high frequency NST, which is probably not center tapped like the old, tar-potted NSTs. In that case, probably perfectly fine to full wave rectify it.
I have the same issue with the deuterium from Cambridge isotopes, so hopefully I'll be able to order through my school.
Good luck!

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Richard Hull
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Re: First Reactor Test

Post by Richard Hull » Mon Jan 05, 2015 7:12 am

I assume that you know that the gauge you have is no good for reading a technical vacuum at all. It will never tell you anything quantitative about your actual vacuum.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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