Another gun I put together

[pfostini]

I know I keep building these things but they are fun. I built this from Farnsworth's design http://www.philotfarnsworth.com/IonGunDetails.html and this too works well. Still no focus but is pretty bright and gets plenty warm. I will take some pictures of it operating in a few days.

[3l]

Wow this investigation is running like a freight train lately....
very nice unit....can not wait for the fusion results from your ion guns and Richard Hull's linear gun work. I've been working on a high current pulse ion gun. I started work on it about a year ago.
I found there was no really good way to couple the energy to my pulsed fusor... but instead of doing more arcing, I decided to investigate the mirror work of LBL the MCX2 series in peticular.
They had designed a pulsed injector that used ECR a pulsed high voltage source and a car like injector to feed deuterium.
They simply fed voltage to filaments and created a large number of high speed electrons in a tight circle. Then a blast of deuterium gas was admitted then the unit was pulsed at high potential to output deuterium ions.

Larry Leins
Fusion Tech

[Richard Hull]

That extractor bore hole looks awfully generous! What is its diameter?

I am looking at no more than 0.4mm for my proposed effort, if and when I crank up. I hope to not have to diff pump the system but obtain an "effective" diff pumped level through extractor aperture control. It can certainly be done. The question is just how well will the system perform in this mode?

Richard Hull

[Starfire]

Phil, what is the function of the discs below the heater in center bottom pic? they don't appear to be connected to anything - or am I missing something?

[Paul_Schatzkin]

Wow.... very exciting to see somebody in the group starting to build/experiment with Ion guns. Seems things are racheting up a notch around here. Nice work.

--PS

[hellblazer]

In my 1962 book on particle accellerators, there's a chapter on ion sources where they discuss the duoplasmatron. The original inventor claimed output currents as high as 500 mA (!) through a 1mm hole. The author goes on to say that later sudies of this on source substantiate this figure, although developments (60's era) have been in the direction of 10 to 100 mA sources with smaller exit holes. Analysis of the ion beam indicates that at least two thirds of the emitted ions are protons.

Naturally, this is with a water cooled design and god only knows how much input power. But the air cooled duoplasmatron link I posted earlier claimed a power input of only 500 watts with a beam current of 10 mA. It certainly seems plausible that careful amatuers should eventually be able to reach an order of magnitude less with about the same power expenditure...

[pfostini]

That picture is the laser header before the mods. I removed those and ther is a cup around the cathode as in the link drawing. The discs purpose is to prevent particles from entering the optical areas of the lasers brewster windows.

[pfostini]

The extractor bore is too big ( 2mm ) but it is what I had. I have tungsten discs but they are not cone shaped. Is the cone a requirment or can a flat disc be used? If the cone is required I could weld a piece of tunsten t the cone. But the idea of using a small orfice would probably work very well. The pinhole would provide the pressure difference needed.

[hellblazer]

I'm still plowing through the ion sources book, but I think the cone shape is pretty much essential to the focussing of the beam. Dave can perhaps talk more sanely about this, but with the flat disc, you have a very differnt field. Basically, another floodlight. With the cone (afaik) you'll have a reasonable beam.

[Richard Hull]

You could see in the Farnsworth images the damage at the extractor cones.

Tungsten extractor inserts are a virtual must with currents in the 1ma and above range. The cone can be made from any thing (almost). It is the actual plasma orifice that needs to be tough. Tim Raney and I are looking at the three best metals for the insert aperture, Mo, W and Ta.

A lot has to do with the extractor voltage. The higher this voltage, the more robust the aperture must be, obviously.

I would like to hit 5kv, at least, in the extractor. At 1ma that is 5 watts of deuterons! I am ready to spend over 300 watts per gun to get those levels.

Richard Hull

[Richard Hester]

You might also want to look at Tungsten-Rhenium, which has almost as high a melting point as Tungsten, but is a whole lot easier to machine. This also may go for spot welding, too.

[3l]

Hi Phil:

Replicating the gun you gave me is a fun thing!
Ok ...How did you mount the BeO tube in the conflat nipple?
Very pretty welding here!
Or soldering?

Happy Fusoring!
Larry Leins
Fusor Tech

[Codecat]

Hi Phil…



I saw your post on this forum, and I must say that I really am impressed with the ion gun that you built! I am interested in building a linear accelerator, and wondered if your ion source would be appropriate for that use. A linear accelerator uses a very hard vacuum as opposed to a fusor, and I am not sure if that would be a factor with this. Another question that I thought of is would this device work with heavy gasses, such as Xenon? Finally, do you make your ion guns available for sale? I do not have any machining skills, and I must say that what you constructed looks like it would take a master machinist from Germany to make.



I have a long way to go with my project, and so far I have been working on the vacuum system and a voltage source (CW voltage multiplier).

Email me privately if you want.




All the best and 73,



Joe Herdler, KB0TXC