Simple Ion Gun Design Revised

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
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Jeremy Adams
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Simple Ion Gun Design Revised

Post by Jeremy Adams » Tue Aug 04, 2015 7:27 pm


I have a new ion gun design, which is similar to my old one but modified. It basically has two filaments with a strong negative bias reducer nearby. Neutral deuterium gas will be shot into the chamber and be ionized by the electron bombardment. An inductor placed outside the chamber will help direct the electrons. This will be accelerated using 4 positive bias rods. Each rod will increase in voltage bias. Magnetic inductors will be used to direct ions.

I've read more on ion gun design, but I still have some questions. What voltage and current ranges should be used for the acceleration of the ions? My understanding is that a high voltage will force ions closer together (because of the perpendicular electric field), and magnetic inductors will increase the speed of the ions. What equations relate to these ideas?

Also does anyone know where to get a glass rod welded to metal for high vacuum research? (I saw items like this in other ion gun design posts here.) I'm not entirely sure how to get a purely positive or negative bias on a plate. It has to be direct current of course, and maybe this includes sending the negative terminal of a power supply to the plate and then grounding it.

Jeremy Adams
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Dennis P Brown
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Re: Simple Ion Gun Design Revised

Post by Dennis P Brown » Fri Aug 07, 2015 1:21 pm

Not sure what you want relative to "high vacuum" but I epoxy glass tubes to metal ones all the time and get in the bottom of 10^-6 torr range. However, metal to glass tube seals (not sure why you ask for a rod) are available from commercial high vac companies and for a price, can even be custom manufactured. Not too difficult to master the manufacture at home of such assemblies with a good welding system, the proper glass tubing and reading up on the subject. The FAQ's here have threads on this topic.
As for what voltage/current to use - well, depends on what you want. To simply ionize deuterium gas is trivial using any cheap high voltage power supply - the issue then is desired beam current (which you haven't in any way qualified). Trying to create very high current guns is a very complex subject and difficult generally requiring a great deal of money as the main ingredient (lol.) There are a lot of threads/posts on this very subject in the FAQ's in this topic area so try searching this subject here rather than blindly asking such an open ended question.
Your question about getting a "purely" positive or negative charge on a plate indicates you really need to read some very elementary books on electronics and/or E&M theory. Hint: you did answer your own question. As for getting ions together, not very easy(ask the tokamak people) and for accelerating, select the voltage that achieves the acceleration you want.

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Werner Engel
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Re: Simple Ion Gun Design Revised

Post by Werner Engel » Tue Aug 11, 2015 5:54 pm

You can also search for the words "neutral beam heating" in the tokamak world. There is currently work in Progress regarding a new design: ... ing_system

In this case the Deuterium ist ionized by a 4 MHz HF Generator, like some others allready described in our forum (Mr. Rapp).

Alex Balanescu
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Re: Simple Ion Gun Design Revised

Post by Alex Balanescu » Wed Sep 30, 2015 12:51 pm

Regarding welding the glass rod your best bet would be to use epoxy. I have welded quite a bit and had a part time job in this field and I can tell you that welding two different materials together rarely works. Assuming there will be pressure put on this weld, it will not hold up. I have welded aluminium to steel and it barely supported it's own weight, I'd hate to think what would happen with glass and metal. Glass on glass would work using a blowtorch.

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Steven Sesselmann
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Re: Simple Ion Gun Design Revised

Post by Steven Sesselmann » Wed Sep 30, 2015 10:30 pm


Check out this old post of mine with a filament based ion source. It's easier to construct than your design above and more effective for fusion.

Most fusioneers haven't realised the importance of negative ions in the fusion process. It is often easier to make a positively biased ion gun, but this is actually detrimental to the fusion process.

There have been several experiments demonstrating this, but few people actually understood why. One of the early experiments was by Frank Sanns, he reverse biased his grids so the inner grid was at ground potential and the outer grid was at +HV and produced virtually no fusion even though the potential between the grids were the same ratio as with a negative grid. Then there is Doug Coulter, he has (I presume) unknowingly got it right, he uses two negative grids one acts as an ion source and he gets heaps of fusion. The problem is our current understanding of physics doesn't explain this phenomenon, so after working on this problem I more or less understand what's going on, fusion is a decay process, just like fission, I have explained it in my paper which can be found at (link below in my signature).

The ion gun design that the late John Hendron and I designed, was built for this purpose, to ionize a gas at negative potential. It does make a difference at which potential you pull the electron off the proton.


The Starfire ion source has a negatively biased filament, and feeds the neutral gas in through an apperture inside the filament, causing the electrons to be stripped off at negative potential. The original ion guns I constructed were limited by the feedthrough to -2000V bias, but lower bias would have been better.

Have fun, stay positive with respect to fusion ;)

Steven - Gamma Spectrometry Systems - Various papers and patents on RG

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