Archived - Make Fusor

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Alexander Reifsnyder
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Archived - Make Fusor

Post by Alexander Reifsnyder »

Hello Fusor.net!

My name is Alexander Reifsnyder, I have just turned 17 and I also just finished my Make Magazine style demonstration Fusor! I tested it fully for the first time today, and it seems that a few weeks of sanding, drilling and copious amounts of epoxy have been worth every moment! I followed the directions pretty closely, and it turned out very well, in my opinion. Shortly after the attached picture was taken, the grid in the middle melted, but it was thin wire, so I expected that to some degree. I had made a thicker grid, but I wanted to wait to see if I could make the thinner one work. I will post more updates as I have them. Please let me know what you think!
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This is a picture of the fusor working
This is a picture of the fusor working
Alexandru_Calburean
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Re: Make Fusor

Post by Alexandru_Calburean »

Alexander,

Great glow, and great looking demo fusor. As for the gauge of the wire you are using, that is a factor but current limiting is what will see to your grid living past more than one run. Also, if you can get access to some, tungsten wire is usually the best in terms of how well it resists melting due to ohmic heating and ion bombardment. Great first run though, by any measure. Good luck in your efforts.

All the best,
~Alex Calburean
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Dennis P Brown
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Re: Make Fusor

Post by Dennis P Brown »

Nice plasma. That vacuum gauge really isn't of much value for a fusor; nice to show that the pump is working but that is about it. Do you have another gauge?
Alexander Reifsnyder
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Re: Make Fusor

Post by Alexander Reifsnyder »

I don't have a secondary vacuum gauge, I just tend to wait for 3-5 minutes before I turn the power on. I am a High School student, so I was on a tight budget, but when I get the chance I will definitely buy a better gauge.
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Rich Feldman
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Re: Make Fusor

Post by Rich Feldman »

Lookin' good there Alexander -- and Happy Birthday!

If you want to add instruments and do some generally useful learning,
I suggest setting yourself up to measure the electrical voltage and current.
It will cost less than a suitable gauge for measuring the vacuum pressure,
and there are FAQs here complete with schematic diagrams.

Don't foolishly assume that the electrical state of your plasma
can be read on the nameplate of your NST or other power supply.
That would be as silly as looking for your vacuum pressure in the pump specification.

"In theory, there's no difference between theory and practice. In practice, there is." :-)
All models are wrong; some models are useful. -- George Box
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Richard Hull
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Re: Make Fusor

Post by Richard Hull »

Your prssure is rather high as theglow is diffuse and not a sphere in the center of the grid, but you are now placed in the plasma club. Thanks for sharing.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Make Fusor

Post by Dennis P Brown »

Keep a close eye on Baratron or thermocouple/Pirani gauges on e-bay and want for a killer deal. This is the best "first" gauge someone can get. The deal must (1) be returnable! (2) Include both a display and detector head. If pretested, that is a plus. I obtained a baratron digital gauge and a readout display for under $80 w/shipping (it was Gov surplus). Deals occur and need to be wanted for. Know what criteria to search under and what max amount you will be willing to pay!
Alexander Reifsnyder
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Re: Make Fusor

Post by Alexander Reifsnyder »

Thank you everyone for all of your input! I replaced the grid with a thicker one, and I applied a lot more vacuum grease to all of the seals. I think that the result is a bit better, and I hope that you would agree. The first picture is the best looking, in my opinion, but the second shows the plasma ball a bit more definitively. Please let me know what you think.
Starlogo.png
Please excuse the dirty glass. It seems that my fusor also doubles as a sputtering chamber for the copper target!
Please excuse the dirty glass. It seems that my fusor also doubles as a sputtering chamber for the copper target!
P.S.
Mr. Hull, do you think that this is better? If not, what would you suggest?
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Jim Kovalchick
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Re: Make Fusor

Post by Jim Kovalchick »

Nice. Your second picture shows bugle formation which means that ion and electron flow are starting to resolve better. You are way past some of the demo fusor plasmas where the glow clings to the grid. Better vacuum and gas control will lead to jet mode. At jet mode you will probably need to be wary of your glass chamber.
Alexander Reifsnyder
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Re: Make Fusor

Post by Alexander Reifsnyder »

Thank you very much! I am very new to this, would you mind telling me exactly what bugle formation and jet mode are? Thanks in advance.
Last edited by Alexander Reifsnyder on Thu Apr 24, 2014 11:14 pm, edited 1 time in total.
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Jim Kovalchick
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Re: Make Fusor

Post by Jim Kovalchick »

Bugle mode refers to the horn or bell shape protruding from one grid hole. Jet mode is similar but the bugle focuses to a tight beam.
Mark Scott-Nash
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Re: Make Fusor

Post by Mark Scott-Nash »

Good job, looks great!
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Richard Hull
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Re: Make Fusor

Post by Richard Hull »

A demo fusor with the grid wires glowing tells all that your vacuum is very poor and that you need more work done on sealing system or that your pump is bad.

Bugle jet mode..... You are seeing the raw beginnings of this in you last photo. As the vacuum gets better, the diffuse glow in the chamber and the halo glow around all the grid wires dies out and a central ball of glowing gas appears inside the chamber. Due to various anomalous differences in grid construction one of the grid openings offers a better electrostatic escape path for jets of electrons and ions and a "bugle jet" is seen to exit the grid.

In a larger fusor the jet "bugles" or fans out as it exits the grid opening due to mean free path issues and scattered ion recombination. In some fusors, at critically low pressures, there may be many bugles appearing as only one at a time dancing about the various grid openings, until finally it settles down to a favored opening.

In "jet", "beaming" or "star mode", a very low pressure is achieved, just prior to extinction, and the glow in the chamber virtually disappears. Only a small bright ball of gas remains in the grid center and thin jets or star rays are seen to exit this ball and radiate in thin beams from all openings of the grid at the same time. These ideal beams heat the chamber walls on impact. Glass, even Pyrex, can easily be locally heated to destruction or to doing major damage to the glass walls. If you achieve star mode in a glass chamber, do not run it for long in that mode or you risk implosion.

Star mode tells all that you have a fusion ready chamber and the vacuum control needed to do the job.

My avatar to the right is a star mode image from an old black and white image taken in 1999 from fusor III. Carl Willis has a fabulous color image of his star mode using deuterium as his avatar. These are the ideal sought in a demo fusor using air and demanded in a fusing fusor.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Jim Kovalchick
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Re: Archived - Make Fusor

Post by Jim Kovalchick »

Here is an image of jet mode. This beam will appear as the bugle focuses with better vacuum and therefore higher voltage. Star mode follows this with symmetrical beams from all grid openings.
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Alexander Reifsnyder
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Re: Archived - Make Fusor

Post by Alexander Reifsnyder »

Here are a few photos from my demo fusor. I still haven't been able to get to star mode, but I think that my bugle formations are starting to become a bit more like jet mode. I am fairly convinced that my vacuum system needs to be better before I get any closer to star mode.
This is a spiral grid design
This is a spiral grid design
This is a thicker spiral, made after the other one melted
This is a thicker spiral, made after the other one melted
After noticing that the shape of the plasma followed the shape of the grid because of the <br />electrostatic forces, I decided to try some shaped grids. This one is a cube.
After noticing that the shape of the plasma followed the shape of the grid because of the
electrostatic forces, I decided to try some shaped grids. This one is a cube.
Another photo of the cube.
Another photo of the cube.
This is a cylinder with multiple bugles.
This is a cylinder with multiple bugles.
Another photo of the cylinder.
Another photo of the cylinder.
I hope that these photos look promising to the more experienced fusioneers!
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Richard Hull
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Re: Archived - Make Fusor

Post by Richard Hull »

This is what a demo fusor is for! Playing with ideas, learning about plasmas, learning about Paschens law first hand and in the real world, not out of some text, though that shouold be the base you start from. You link voltage, pressure and current to what you see in a way that will help you move forward.

I spent a full year with fusors I and II, 97-98, just working with this experimental phase. I also co-jointly read "Ionized Gases", one of the best treatments on the subject.

I was in no rush as there was no fusor forum extant, no neutron club that just had me itching to join and no group of amateurs anywhere working on a fusor. I was it, back then

Good effort! Good luck.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Archived - Make Fusor

Post by Dennis P Brown »

Those are really great pictures and that is excellent work! Your glass walls are getting hit by the plasma - the metal coating on the glass walls (can see the dis-coloration; most likely by formed by sputtering action of ions hitting the electrode) means the glass is being eroded and damaged. Be careful and surround the glass chamber with a wire mess (and the mess should have its own ground!) - that way, if a small crack develops and the glass suddenly fails, you will be better protected. Also, always wear eye protection when around glass under vacuum!
Alexander Reifsnyder
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Re: Archived - Make Fusor

Post by Alexander Reifsnyder »

Thank you Mr. Brown. After the first few runs I installed a metal shield almost all the way around the chamber, except for about an inch an a half. In that spot a put a sheet of borosilicate glass so that I can observe it and take pictures. What you see discolored is actually the metal shield anodized from the electron beams. I think that this should protect the glass chamber, but I like the idea of a wire mesh to catch most of the debris from a potential implosion. I am always wearing a full welders mask to make sure the UV isn't hitting my eyes in excess, and when I can I am mostly behind a wall. Thanks once again for your helpful suggestions!
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Dennis P Brown
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Re: Archived - Make Fusor

Post by Dennis P Brown »

UV isn't hitting my eyes in excess, and when I can I am mostly behind a wall.
Great idea and frankly, I missed that hazard entirely. While most glass will not transmit hard UV, some soft UV and certainly a lot of far end blue will get through and most people not into eye safety do not realize that far spectrum blue light is very dangerous as well. So the welding shield is an excellent idea - of course, some people use fused quartz windows and those DO fully transmit the very damaging hard UV spectrum.
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