The next build - ion trap

[Doug Coulter]

Learning - I find it hard to stay on topic myself, so I moved this build info from theories and speculations to here where at least it's kinda on topic. Learning to moderate myself...

Whew, finally found all the leaks. A couple very tiny ones were ... not easy. But on consideration, what I want to do will be quite the ship in a bottle issue with a 2.75" cross, so, casting about, it was decided to use Bill's old fusor tank - an 8" CF flange tee, making the necessary adapters and various bench mods along the way. I had at one time another a long tank, 6" with all QF fittings, leaked a little, had some O ring diffusion loss issues, and well, after storing it and stupidly leaving one port open in a storage building... mice... nests, pee and poop - the real killer, even ate some of the stainless.
Now that old 8" CF tee had some issues too, but was stored better, so no mice issues, and with minimal work, might be really good for this, with the pump station under the bench, the pump line extending through the bench to the tee and a nice working setup (I hope).

I took a bunch of pictures while deciding with Bill what to do next, so might as well share - these are compressed a bit because I emailed them in that form, if someone wants real resolution, well, these are 9 megapixels (the lowest setting on the new camera) and kinda large.

Bill's old fusor tank, which needs some work, but basically is good.

The flange with the HV feed thru is one we made way back and O ring sealed as the CF flange was dinged up at 3 and 12 o' clock. Now that I have some more confidence with my tools, I might just try to fix those dings, and put a modifiable real CF blank back on there - these experiments probably won't need extreme volts, and if they do, well, that's not that great a feed thru anyway.

Closeup of the back flange. The big gap accommodates an O ring.

There are dings in the knife-edge at 3 and 12 o'clock

But if I put on my Clickspring hat and make a couple of custom tools....I might get this back to CF and lose a bunch of inches of water vapor-diffusing viton.

I'd wanted to reuse this, but..

The nicer part of what was inside for a year or two

Just too nasty in there, even after a simple flush and wipe. That'd take a week to really clean up.

Soooo. At the other end of the planet, I have this cute little 60 l/s pump station with a ISO K 63 flange, now to adapt.
To this:

Killed the leaks, the cross is simply too small for what I want to do here.

Full rez for this one. That cross is too small for me to build things inside of it.

[Doug Coulter]

After measuring, it looks like that pump station will fit on the under-bench shelf, and with a couple supports, and an adapter from the ISO to the CF flange, allow the tank to sit just above the bench and be easy to work on. That will leave just the QF flange for the pump, one I have to add for the gage (it's a pkr251 but with a QF on it) and the fast-entry window we made for Bill's tank as O ring seals. We ought to hit say 5 e-7 mbar here - and I don't need it quite that good, but it's always nice to have some wiggle room.

So, I got out my big-boy tools, and re-bored the hole in an 8" to 4.5" CF flange adapter to accommodate a KF nipple for welding. For me, that was the first time changing a cam-lock chuck on my lathe, not as big a deal as I thought other than cleaning things up a bit as too-long disuse had left a bit of corrosion on it, and I gained a whole new level of respect for guys like Abom79 and Keith Fenner being able to zero in a 4 jaw chuck in under a minute - I got to 2 mils pk pk runout in under an hour...sigh. I needed to take off just 20 mils (10 mil cut) on that center hole partway through to allow the ISO nipple pipe to enter the hole...Gee, I think I'll practice my TIG welding on thin to thick too before I weld this.

Came out decently for a first try.

All plastic wrapped till welded. Hope this saves me a few hundred bucks...fingers crossed.

The bench top will probably be around in the middle of this adapter, with the pump below and the Tee above the bench.

So, waiting a couple days for some TIG accessories to come from Amazon, then we'll get going better. That little pump station won't hold up all that weight, so I'll be making some chunks of 2x10 wood with half rounds cut out to hold up the tee so the pump station dangles about an inch of the under-bench shelf - it'll hang fine, but then I'll put in some foam rubber or batting to make it happy and get the vertical force about neutral. Not sure where I'll weld in the QF adapter for the vacuum gage, or whether I'll cut up that nipple from the other tank, or just flat make one from scratch on the lathe (I've done that before and it comes out fine). So, another day, another couple things moved ahead. The main thing really was deciding how to proceed. I think I've learned some lesson that before the fun science part, you gotta build the right tools and setup a good working situation you can mostly ignore to get on with the real deal. This is...that part.

Well, learning some new machine-shop stuff is cool after watching so much of it on youtube...new skills in the back pocket are always nice.

[Doug Coulter]

Oh, lookie - there's a new hole in my bench upstairs, and a flange in it that connects to vacuum!

Moved the pump station to the under bench shelf

The pump moved down to the shelf under the bench.

Now at my feet, still convenient.

Which makes room for more cool stuff up at my working level.

Partial mockup.

Basically, the adapter to the pump station needs to be welded, and the niftier stuff from the 6 way cross on the bench transferred to what is now going to be the experimental tank, and I may even put in that funny looking thing I built sitting next to the cross. It's a mechanical push-pull-twist manipulator using really strong NdFeB magnets. Not sure how I'm going to do gas inlet. My sub 1 bar regulator is on the big tank and even at 1/3 bar, the smallest pulse of gas I can put in is "too big a chunk" in the big tank - takes about 8 pulses from hard vacuum to get to 100 times where I want to start this set of explorations, and this tank is to say the least, a lot smaller (the big guy is 16" by 30" or so ID). Otherwise, all the right stuff is here, and I do have a regulator with the right type connection for hydrogen, just not a fancy super low output pressure one (and really, I need much lower than the fancy one from Massey anyway - or a truly amazingly small leak valve. After all, I want to start around e-5 or so mbar...that's not a lot of gas. I have the same solenoid valve gas "outlet" between the turbo and the forepump as on the big guy - it's just that this turbo is 60 l/s and the big boy is 512 l/s..
On the other hand, even though this turbo is "larger per tank volume" in some sense, it isn't per sq area, and this forepump is roughly an aquarium air pump turned backwards, so the outlet shouldn't be hard to regulate. Same programmable turbine speed as well.

And yay! I found a QF-40 to 2.75" CF adapter already made up and known good. Now, that gage emits a lot of magnetic field, so I may have to devise some kind of shielding, or even a cancelling hemholtz type of setup for it...it was enough to really twist up ion beams etc on the tank it came from if too close to the action.

[Doug Coulter]

Now, there's no way that little pump station is going to be happy holding up that Tee, which weighs in the "bag of concrete, will not lift willingly" range. So, while waiting for consumables and looking for an excuse to practice TIG welding before doing the all important adapter - I modifed a couple of turnbuckles that had been hanging on a peg here for nearly a decade, cut the chain hooks off the end, and TIGed on some metal to make little vacuum oriented machinist jacks, so the weight of all those 8" flanges etc can be mostly supported by the table instead of the turbo pump mounted on the sheet metal top of that pump station.

These can go under the ends of the tee and hold most or all of the weight.

Not shown is some other shop work to shorten that adapter nipple a couple inches, and make provision for one of my gas inlet micro solenoid valves to mount to the side of it - save those big flanges up top for things that change more often or need that much of a hole. It'll show up in future pix (over and over, no doubt).

Yes, that's the old microwave ion source in the back...some version of that might get adapted - perhaps I can use the ISO<>CF adapter as the resonant cavity - because nothing else has ever worked as well as that down to the low (sub e-6 millibar) pressures. Maybe an electron flood of an area would do as well, but that's its own can of wigglies.

[Doug Coulter]

I have a hopefully entertaining video in the making about finding and fixing the leaks in this, but crashy video editors (kdenlive/openshot) and my lack of learning the ins and outs are holding that up a little bit.
In the meanwhile, I had a little fun this AM with some dry nitrogen and a discharge vs pressure video - I should have started this at much higher pressure where there was a more or less visible straight path between electrodes, dark spaces appeared and all that, but it is what it is. More later of course.
https://www.youtube.com/watch?v=AbB9NhgOHnY