COMSOL simulation of a FUSOR?

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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ian_krase
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Re: COMSOL simulation of a FUSOR?

Post by ian_krase »

They certainly are more complicated than a basic fusor, since an ion source is unavoidable, but the Rapp Instruments beam on target system seems *very* simple, with the only really more complex issue with it being the need for a (slightly) higher vacuum than a fusor and an auxiliary power supply (which can be a cheap NST supply).
Last edited by ian_krase on Sat Sep 23, 2017 5:28 pm, edited 1 time in total.
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Richard Hull
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Re: COMSOL simulation of a FUSOR?

Post by Richard Hull »

A good ion source, deeper vacuums, and the need to either load or purchase D2 loaded targets stop virtually every amateur from beam on target systems. Only a very few have tried it. most of them did fusion first with a fusor. No one here has reported activating silver with beam on target.

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Re: COMSOL simulation of a FUSOR?

Post by ian_krase »

Thomas Rapp claimed (on his own site) to have successfully activated indium and silver with neutrons from his beam-on-target machine; I don't know if you consider it well-substantiated, and his ion source is ultra-simple.
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Richard Hull
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Re: COMSOL simulation of a FUSOR?

Post by Richard Hull »

Here at fusor.net we have rather rigid and rigorous reporting standards, so I do not know about his system.

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Re: COMSOL simulation of a FUSOR?

Post by ian_krase »

His beam on target reactor is here: http://www.rapp-instruments.de/Beschleu ... neugen.htm . He measured with both a scintillation counter and with activation.

Three things are notable to me: first, the extreme simplicity of the system. Second, the interesting arrangement of a "suppressor" collar around the target and the associated capacitative glow discharge based current meter, which measures currents in the microamperes while floating at +100 kV. Third, the fact that he uses an extreme-voltage (100kV plus?) but apparently low-current power supply.

I am intending to build something like this, though with a less powerful 50 kV supply.

(I am also intending to replicate some of his mass spectrometry experiments).
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Richard Hull
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Re: COMSOL simulation of a FUSOR?

Post by Richard Hull »

100kv is far beyond anything ever done here but the microamp currents seem incongruous. An interesting system if you have the voltage to pump it and can afford to buy the target or have the where with all to load your own.

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Re: COMSOL simulation of a FUSOR?

Post by ian_krase »

Huh. I thought he loaded it by bombarding it with the same D2 as was in the accelerator, similar to how fusors get their walls coated.

Is there a reason to think that either this or a colliding-beam variant of it would not work with 50 kV?
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Re: COMSOL simulation of a FUSOR?

Post by Dan Knapp »

I just came across a finite element modeling software package you can use for free: simscale.com.
Anything you do in a free account is visible to the community of users, but the price is right. If you want to keep your work confidential, you have to open a paid account.
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Richard Hull
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Re: COMSOL simulation of a FUSOR?

Post by Richard Hull »

It would be interesting to see which system would do the best per unit input power, provided each system had the same demanded, tight controls in reporting. Something that seems unlikely.

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Dennis P Brown
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Re: COMSOL simulation of a FUSOR?

Post by Dennis P Brown »

As someone who built an accelerator (deuterium) and a fusor, I only succeed generating successful fusion with the fusor. I have never actually "fired' up my accelerator (despite the fact it is essentially 100% complete - sigh) because obtaining the high voltage via a Van de Graaff was a terrible approach (built two units; one very large - fun exercise but wasted effort.) Guess I should see how they solved the high voltage issue so thanks for the link (they show only a 25 kV supply (how does that do fusion?!); I don't read German so where is the design for 100 kV?)

I have also built a successful and rather high current voltage multiplier but it tops out at 60-70 kV (no easy way to double that to what my electro-static lens would need to really function. However, that supply would likely work for a simple ion gun neutron generating system;) but back to the main point, that supply is absolutely deadly so I never tried hooking it up to the accelerator (besides not being high enough voltage for the lens, the head assembly containing the gun/gas supply/gas ionization system is far too large of an exposed area to safely energize and be around/operate with that deadly supply - just too risky since I have a working fusor, anyway.) Didn't stop to consider that issue until after I built that monster supply ...lol.

But then, I do like building these types of projects for both the fun of it and to learn the in's & out's of these devices as well as to better master the many skills needed to work in high voltage/vacuum systems.

If one has the time and interest, these types of "side projects" can be very useful if not, somewhat irrelevant to directly building a fusor. I will say that without the numerous side projects, I'd never have obtained the skills and knowledge needed to build a working fusor; yes, the information provided by the people here was absolutely critical but I really did need to build smaller, simpler projects before tackling the monster called a fusor.
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Re: COMSOL simulation of a FUSOR?

Post by Daniel Fajardo »

Hello Werner,

Its funny you asked this question just now. I'm about to finish my demo fusor and want to start working on a simulation in COMSOL.

I'm thinking about simulating the electric field and particle tracing. I'm not quite sure how to make the grid geometry, though.

Please let me know if you have worked on something. I would love to share ideas with you.

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ian_krase
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Re: COMSOL simulation of a FUSOR?

Post by ian_krase »

Thomas Rapp's beam-on-target machine (he actually built two) doesn't use the 20kV to do the fusion. Rather, that is just used to drive his canal-ray ion source.

He is also ballasting the living daylights out of this (100 megaohms!) so likely he isn't even getting near 20 kV in operation. Not sure why he didn't just use an NST.

In any case, the small test-tube-looking appendage is the ion source. The pipe tee is at ground potential, and the terminal on the end of the ion source is at +20 kV. D2 is piped into it and the glow discharge ionizes it. The E-field extracts D+ ions into and through the pipe tee and into the long, large glass column, which is at a much better vacuum.

His initial tests just had the resulting canal beam hitting the end of the column which cannot have been easy on the glass. Later on, he replaced the end of the column with a target holder and secondary electron suppressor, and applied -100 kV directly to this target holder, with the glass column serving as an insulator).

Why do you have your ion source at high potential?
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Samuel Low
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Re: COMSOL simulation of a FUSOR?

Post by Samuel Low »

I don't think COMSOL has a module to do particle tracing unlike SIMION. I know for sure you can definitely run an electrostatic simulation to see the spherical E-field patterns - the usefulness of it would really then be the ability to just see the E-field patterns for different CAD models of inner grids. It would be very interesting to see the effects of various inner grid geometries, I would love to see some screenshots with the colour bar scale if you ever get to doing the experiments! Good luck! :)
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Re: COMSOL simulation of a FUSOR?

Post by Andrew Seltzman »

I believe comsol does have a particle tracking module, but it has to be licensed and installed separately and is not part of the basic package.
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