Nathan Marshall - Fusor Progress

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
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Nathan Marshall
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Nathan Marshall - Fusor Progress

Post by Nathan Marshall » Fri Mar 27, 2020 3:13 am

Hello all,

Back in 2013 when I was 13, I learned about amateur fusor construction. Since then it has been my goal to build a working fusor. When I was 14 I made a simple demo fusor in a bell jar with an HVAC pump. It was extremely crude and extremely unsafe... but it glowed real nice! Since that time I have worked on many other projects relating to vacuum and high voltage, and I have slowly been accumulating knowledge on the subject and high vacuum parts to make a real fusion attempt. I no longer had easy access to my parents' basement where I worked on my projects once I started attending college in 2017. Between dual majoring in physics and chemistry, club activities, undergrad research, and summer jobs, I have had little time to work on my fusor besides school breaks. I find myself back at my parents' house now due to online classes as a result of the coronavirus. So lots of time to work on my fusor until my internship starts this summer!

Attached are some pictures of my vacuum setup and first plasma images. The vacuum pump is an Edwards E2M2 that was being thrown out by my university's engineering department. It was in nasty condition, but after some cleaning and oil flushes it pulls a deep vacuum. The HV source at the moment is just an oil burner ignition transformer running through a couple microwave diodes. It does the trick for producing some pretty demo plasma! The grid is 0.02" tungsten. One of the rings is a bit out of alignment in the plasma pictures. This will be fixed as I am currently making a more robust grid holder. I also plan to use four rings instead of three. The diffusion pump is an Edwards Diffstak 63.This past summer I took it apart and cleaned out carbon deposits on the jets from whatever setup it was in before I acquired it, so it is clean and ready to pump down. Vacuum measurement at the moment is with an Edwards APG-M on the foreline. I have a Varian ion gauge on the main chamber, and I'm currently building a custom cable to connect it to an MKS 919 controller. After I have that connection made I will begin high vacuum tests of the chamber. Next up is deuterium addition and the construction of a proper 30kV power supply. I have a deuterium bottle, but I still need to get the regulator and make a flow restriction setup. More progress to come!
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John Futter
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Re: Nathan Marshall - Fusor Progress

Post by John Futter » Fri Mar 27, 2020 6:35 am

Nathan
nice setup
not sure you require the fancy banyard alpert gauge head but good find
your demo pics are first class

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Richard Hull
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Re: Nathan Marshall - Fusor Progress

Post by Richard Hull » Fri Mar 27, 2020 8:40 am

Nathan, What the heck is all that burple and pink stuff going on? That is not normal, I would think. They almost look like leak streamers!

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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Nathan Marshall
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Re: Nathan Marshall - Fusor Progress

Post by Nathan Marshall » Fri Mar 27, 2020 12:26 pm

John -
Thank you! I got the ion gauge with a gauge cable for $30 which seems like a steal price. The filament still has continuity, but I have yet to test complete functionality. Hopefully I can get to that within the next few days when I make the proper connectors on the other end of the cable to connect to an MKS 919.

Richard -
Are you referring to the squiggly lines in the plasma pictures? Those are reflections of the grid glow. I’m looking down a length of 2.75” conflat with the viewport and camera, so I’m getting reflections from the inside of the tube in the picture.

For example, here is a picture of the fusor grid still glowing after the HV was just switched off. The reflections are really neat!
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Richard Hull
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Re: Nathan Marshall - Fusor Progress

Post by Richard Hull » Fri Mar 27, 2020 9:55 pm

Man what a cool idea and polished system. I have never seen a mirror finish in any fusor system here, ever!!! Nice.

Joe Zambelli, back in 2001, had a mirror finish externally. Also, the only one of those I have ever seen.

viewtopic.php?f=55&t=11184&p=73754&hili ... lli#p73754

Thanks for the explanation.

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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Nathan Marshall
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Re: Nathan Marshall - Fusor Progress

Post by Nathan Marshall » Sat Mar 28, 2020 5:51 pm

Thanks Richard! Wow, Joe’s fusor is a real masterpiece... a beautiful finish on that and perfect flange placement. I have to admit that the mirror finish on the inside of mine was a bit unintentional, the chamber that I got off eBay happened to have a pretty slick finish on the inside.

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Richard Hull
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Re: Nathan Marshall - Fusor Progress

Post by Richard Hull » Sat Mar 28, 2020 7:52 pm

Indeed!! Someone, the original recipient, paid a gang o' bucks for all that internal polish. It is rather obvious it was never used to retain that polish. Maybe paying for it broke the back of the project. The thing looked medical grade inside. Musing wildly, could it have been used to test pathogen survival over lower pressure or near space vacuums?? This would mean that if it saw medical use its shine would not have been impacted. Not to worry, the instant you got a glow, any nasties would have been wiped out. A most interesting construct for sure.

Coating places might have ordered it so that once their specific coating polluted the thing that would be all that ever entered it as they would keep it under 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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Nathan Marshall
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Re: Nathan Marshall - Fusor Progress

Post by Nathan Marshall » Thu Apr 09, 2020 1:42 am

I snagged an MKS 127AA-000.1C heated baratron for $60 on eBay. This has a full scale reading of 0.1 Torr, and a 1.33" conflat inlet! Perfect! I made a little power supply unit with a 24 VDC switching supply and a CCG154815D module that puts out symmetric +/- 15 VDC. I used a DB-15 breakout board and a cable to connect the supply to the baratron. It takes about 45 minutes for it to get up to temperature, not bad at all. I am happy to have a gas independent pressure gauge! I'm using my DMM at the moment to read the 0-10 VDC output from the baratron, but I plan on getting a cheap one from harbor freight to use as a dedicated readout for the gauge. So far the baratron works perfectly! I'm also working on a more robust grid design, a deuterium addition system, neutron detection with a Russian SNM-12, and the high voltage power supply. Things are coming along great. I have a month and a half until my internship starts... hopefully I can get some neutrons before that begins! My classes are all online but still no less work, so I have to make sure I don't put too much focus into my fusor. We recently studied potential gauge theory in my electromagnetic theory 2 class. Couldn't help but snicker at the idea that I am working on some "gauge theory" with my fusor ;-)
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Nathan Marshall
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Re: Nathan Marshall - Fusor Progress

Post by Nathan Marshall » Tue Apr 21, 2020 3:20 am

I got the chamber outfitted with a conflat to swagelok adapter. I put a low flow metering valve and a hydrogen regulator on the line, and now I can tune the chamber pressure! I still haven’t hooked up the deuterium tank. I’ll wait until I’m ready for fusion and neutron detection. Also, I’ll add a shut off valve in the line as well since the metering valve doesn’t seal completely. I tuned the pressure to about 100 mtorr and got this beautiful star! The grid has been improved using a set screw coupler and a piece of copper to crimp the tungsten rings together. See this thread for more details on the grid: https://fusor.net/board/viewtopic.php?f=6&t=13364
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Mark Rowley
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Re: Nathan Marshall - Fusor Progress

Post by Mark Rowley » Tue Apr 21, 2020 5:23 am

Very nice!
What is the diameter of your grid and inner diameter of your chamber wall...or closest point to the grid?

Mark Rowley

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