Archived - Star Mode (American University)

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bk8509a
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Archived - Star Mode (American University)

Post by bk8509a » Fri Mar 19, 2010 4:59 am

Recently our 30 year old HV supply died, so we had to get a new one. We picked up a Bertan 30KV 10ma constant power supply. I was worried it wouldn't perform, I was wrong.

After a week of twelve hour days in order to prepare for the university's research conference, I'm excited to give you these pictures.

All pictures are taken around 6 mTorr, without a pump running. We then turned the HV supply on to constant current mode at 10mA. All of these runs then ramped up to a parabolic peak of around 25KV and then back down to around 19KV. At the same time the pressure went up to around 9 or 12 mTorr. We were too scared to go any higher of a voltage. Were completely surrounded by lead bricks, but the Geiger counter screamed when we put it in during a pulse.

I'm also excited to say that we created a complete data logging system on Labview, which exports our data into an Excel file. We are capable of recording voltage, pressure, current, and counts. If anyone is curious to see our VI, or our 100 data points a second (better to have too many than too few), send an e-mail.

In short, here our results. If you asked us last November if we would be here, I would have said no. In these pictures you can see star modes.

I would like to point out that in the highest voltage pulses I believe an e beam is hitting the window. I thought it was glare, but I turned off each light in the room. It does not appear at lower voltage pulses (last picture). Not good for my view port, but I won't take it up as high anymore. In some of those pulses where you see the e-beam you can also see the reflection of the box our camera sitting on (straight line on the bottom), which is engulfed by lead.

For all of you who are NOT using shielding at voltages higher than 15KV, please, please, invest in a Geiger counter.

Next stop: Langmuir probe!

NOTE: This is in air plasma, not Deuterium. We'll never make it to the neutron club because the university forbids us making that radiation.
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myID
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Re: Star Mode (American University)

Post by myID » Fri Mar 19, 2010 5:09 am

Congratulations!

Some pictures of the whole setup and some more details would be nice. What kind of pump? What chamber? Could be you already posted it somewhere else but might be also worth it to add it to this posting I think?
What are your Future plans? Neutron production?

Kind regards
Roman

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Carl Willis
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Re: Star Mode (American University)

Post by Carl Willis » Fri Mar 19, 2010 5:30 am

Hi Brian,

Very nice photos. Congratulations to you and the rest of the team. Now it's onward and upward, with fusion hopefully to follow soon.

Is there any D2 in there now? What are the counts from that are recorded in LabVIEW?

You can post Excel files here if you want, although there is a pretty restrictive size limit on the fusor.net server.

-Carl
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Doug Coulter
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Re: Star Mode (American University)

Post by Doug Coulter » Fri Mar 19, 2010 2:34 pm

We get the electron beams hitting the glass effect too and it can be nasty, not to mention browning the glass -- put a sacrificial piece inside your window to take that and maybe even cover it with conductive screen, grounded (which makes the in tank field more uniform anyway). You can of course have a little fun verifying the polarity of the charged particles with a small magnet near the window. Good old right hand rule right there where you can see it to have some fun.

Yes, X rays are one of the bigger places any lost energy in one of these winds up (right after heat). You don't need real thick lead to stop ones of power supply voltage/energy though -- a couple mm will do -- but it has to not have holes and leaks! Anything that gets through say 1/8" thick lead isn't one of those, it some byproduct of fusion. There is a third branch of the DD reaction that just goes to He and a very hot gamma in the 13 mev range -- that one you're not going to stop easily, but that branch is 1::10,000 of the more common two reactions so there aren't that many of them. My rad safety rules from some government agency say that even the thin lead will do to 75kv and better. But when you scale that to megavolts, well, the lead gets to be really thick. Which I suppose is why Farnsworth and pals just put the thing in a pit and monitored remotely once they had it really working well.

You will notice dramatic changes in operation parameters if you ever smooth off all those sharp edges I see from wire welding....and over time, sputtering will do that some too. Just a heads up on that so ti won't be such a big surprise when (not if) it happens.

You can get to pretty good fusion rates with 30kv and 10 ma, but more volts and perhaps less current would do better, or it does here. This basic design seems to respond more to subtle things than just "cranking it up to 11".
Why guess when you can know? Measure!

bk8509a
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Re: Star Mode (American University)

Post by bk8509a » Fri Mar 19, 2010 2:51 pm

Doug,

Thanks for the idea of putting a crap piece of glass in there. I'll definitely do that. I'm not going to test if the e-beam is an ebeam with a magnet because It would require me to put my hand near it during operation.....that's not going to happen when i'm getting 350,000 CPM in a 4 cm^2 region

Shaving off those wire welds is going to be a huge pain in the ass, but we can do that. This was our second spherical outer grid that we made. It sucked making it. I do think that it is distorting the electric field though, and heavily.

I did all my own x-ray calculations using NIST data, which I should probably post on this website. Its good to calculate x-rays in and x-rays out.

I'm going to edit the original post, but sadly, I will never make it to the neutron club. my university is forbidding me to make neutrons, therefore I'm using N2 and O2 and whatever else is floating in the air. It still is going to yield great results.

I'm in the process of building a heavy duty Langmuir probe for plasma measurement. I'm going to post a guide for that when i'm done.

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Doug Coulter
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Re: Star Mode (American University)

Post by Doug Coulter » Fri Mar 19, 2010 4:01 pm

Yeah, the extra piece of glass is a good thing here, and it cuts the X rays in half.
Personally, I wouldn't worry that much about sticking a hand in there momentarily. You're talking putting in half the volts at perhaps 1/6 the current of a "real (efficient)" X ray machine and those don't kill too many people. So you've got both less quantity and less quality (energy) X rays than in a hospital, the danger here is more like it can go on for a long time -- so, don't stand in the beam for a long time!

I won't say the sharp corners are a 100% bad thing -- they seem to help the thing get started easier, my theory being a tiny amount of field emission off them gets the ball rolling easier. But they do whack the field shape nearby. I used Ti wire, .030 for a lot of my early work (and still use it some) and that's not hard to make grids out of and then smooth off -- McMaster's version is pure, so is fairly soft and easy to work with.

We finally put a piece of lead glass over the whole viewport outside that stops them *all* so no more worries here. Our first version of that was a faceplate busted out of an old TV crt, and that worked fairly well -but was dark. The new version is fairly thick clear leaded glass from a hospital radiology room, and that really stops them all and is clear -- the geiger counter sits on the background reading.

AU is that backwards now that they won't let you make fusion? My Dad went there for his Physics degree, sorry to hear they kind of lost it since. I got mine across town at CU (that other religion) and they let us do cool things indeed there -- some actually dangerous (even by the standards of some of the more laid back here), but this was all before the nanny statists really got going. There I filed Be with sandpaper on my desk at my advisor's request, and during numerous plasma pinch experiments exposed quite a lot of X ray film with X rays glancing off a NaCl crystal -- film was 10 feet from the pinch, I was 3 feet away to run the gear...so, pretty good dosages, and here I am still.

You going to put your probe on a wobble stick? That would be fun. I made a pinhole camera for charged particles and X rays (sees mostly the particles though) that I put in there and play with sometimes -- getting ready to add electromagnets to it so I can shift the part of the image that is due to the particles vs the part that is X rays. There's a pic of it (not a real good one) here:
www.coultersmithing.com
The actual resolution is better than that, but the phosphor on the screen makes the digital camera bloom, it's so bright. What's fun is how the picture changes as you move the thing -- the particles aren't all going in straight lines at all...and there are variations in densities of them (beam like) the camera will intercept or not depending on where it is. Guess I'm going to have to make a movie of that, it's very cool and very hard to put in words well.
Why guess when you can know? Measure!

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