We Have a workable Ion Gun

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
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pfostini
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We Have a workable Ion Gun

Post by pfostini »

I went into work (again) and made another test bed. This time for the modified laser tube gun we made in the Ion gun construction/proposition post. The gun is the one that I posted last on that thread. I put the multipactor aside for now because I need to make an rf supply for it.

I do think we have a workable design and we need only to focus the beam now. The reason I say this is because the beam is at least as wide as the quartz plate I am testing with ( 15mm) .

The cathode only has 12 AC amps on it. The ionizer electrode has +650 volts on it. I found a use for my switcher . I am using it as the accelerator voltage of about -4KV. I attribute the higher voltage due to the long bore length of the tube. The small .040 inch bore does not seem to ba any problem.

The unit runs VERY stable down to 4x10-5 torr and I adjust the guns power with the accelerator current.

Now I will try Hals measuring circuit to see what we can deliver. I thing a small electromagnet on the ceramic bore towards the accelerator electrode may give us some focus.
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Mark Rowley
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Re: We Have a workable Ion Gun

Post by Mark Rowley »

Outstanding job !!!! Only if I could have the time to do such things............

Mark Rowley
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Starfire
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Re: We Have a workable Ion Gun

Post by Starfire »

Congrats Phil -- great work
hellblazer
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Re: We Have a workable Ion Gun

Post by hellblazer »

This is very cool.

I want to be Phil when I grow up.
hellblazer
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Re: We Have a workable Ion Gun

Post by hellblazer »

I think Richard's idea for the accellerator might be useful - in reverse, strangely enough.

I saw a diagram of an electron gun which did a very interesting thing. The beam was diverging, as the ion gun's is, so the beam through a negativly charged cylinder to squeeze it back into a beam. So, in the ion gun case, after it's left the negative accellerator, perhaps a positive cylinder would squeeze the beam back into shape. There's the lensing effects of the two charged cylinders which would undoubtedly do something weird, but something like Richard suggested might work, except using a positive charge, rather than using it as an accellerator. The ions would want to be in the center while still being accellerated towards to the fursor cathode.

Might work.

Anyways, I've discovered the magic of Torr Seal, thanks to you. For someone who isn't the greatest welder in the world, this stuff is a god send! 10-9 isn't shabby, and makes a world of difference to my ability to start doing similar experiments. Many thanks for the inadvertant tip.
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Richard Hull
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Re: We Have a workable Ion Gun

Post by Richard Hull »

Torr-seal is fine as long as you can warrant no electrons or ions ever hit it (gross outgassing) and that you can keep it cool (not high heat friendly). Remember, it is just an organic. It ain't steel. Be very careful where you use it in a system.

I try to locate it inside of machined groves for marginally tight fits so that it will not actually wind up in the vacuum chamber, per se. It is fine to slather it on the outside of fittings and stuff but looks butt ugly.

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
hellblazer
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Re: We Have a workable Ion Gun

Post by hellblazer »

Many thanks. This is kind of what I figured. I have no problems with the machining of things, it's just my TIG welding needs far more practice to be vacuum worthy. A little bit of machining and some epoxy can go a long way to making up for that. Still, I'm trying to get better at TIG welding as in the long run...
r_c_edgar
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Another sealant

Post by r_c_edgar »

Heard of Vacseal?

They make some pretty impressive claims (very high temperatures, extreme vacuum compatibility), and I've heard only good of it. I'll probably buy a bottle sometime to see for myself how well it works.

Of course, the caveat of keeping it out of the way of charged particle beams still applies.

--Ryan
hellblazer
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Re: Another sealant

Post by hellblazer »

Many thanks. This is definitely interesting stuff. Not quite structural epoxy, but some very interesting uses...
Richard Hester
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Re: Another sealant (Vacseal)

Post by Richard Hester »

Vacseal has covered up many an "oops" in UHV systems. It's clear, so no one knows you screwed up...
The cure times at room temperature are very slow to attain UHV levels, but don't be fooled, the stuff dries to the touch in a few seconds. I tried using some to make ZnS phosphor screens, but it dried too fast. A slurry of phosphor, Vacseal and appropriate solvent would have worked better. I'll let everyone know when I find out what the major solvent component is.
The stuff comes both in a bottle with applicator and a spray can.
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Carl Willis
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Re: We Have a workable Ion Gun

Post by Carl Willis »

On the subject of Torr-seal, I believe that Hysol Epoxi-patch 1C is nearly
equivalent to Varian's epoxy and is much much cheaper. I have used Hysol 1C in
vacuum on many occasions and, as long as temperature extremes and ion beams
avoid it, it performs very well.
Carl Willis
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TEL: +1-505-412-3277
JohnCuthbert
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Re: Another sealant (Vacseal)

Post by JohnCuthbert »

The material safety data sheet on the vacseal website gives the ingredients and I think they are usually listed with the dominant component first.
hellblazer
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Re: We Have a workable Ion Gun

Post by hellblazer »

That's what I picked up. Dunniway's price isn't to bad.
Richard Hester
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Re: Another sealant (Vacseal)

Post by Richard Hester »

The MSDS gives the hazardous components of Vacseal, but does not say which solvent is the dominant one. Another site says that wet Vacseal can be cleaned up using toluene, but the dried resin requires a nastier solvent like MEK or methylene chloride. It sounds like the stuff could be thinned with toluene, which is preferable (but not by much) to using perchloroethylene or methylene chloride, two of the other nasty solvents contained in Vacseal.
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