Faulty parts

The materials didn't come until 3:00 today, and when they did, we were told that the plastic we got for the rod is too soft to machine. We ordered a new rod made out of a different plastic, and it should come tomorrow; the time that it comes, and the availability of the machinist, will determine whether I will be able to assemble and install the device tomorrow or if I'll have wait until Monday. The latter would be pretty unfortunate. Yesterday I was able to get a cloud only 5 hours after the chamber was at atmospheric pressure, but of course I don't want to spend Monday pumping the chamber and baking plasma. I installed the plastic rod we had anyway, so just to see how it looks:

The red markers show the ports that I initially intended to use for the rod, on the same level as the top electrode. I'm a bit annoyed at whoever designed this chamber, though, since the conflat of that port (the thing attached to the opening) is too close to the large side ports to attach anything to. As far as I can tell, the only thing it could be useful for is for routing wires, because literally nothing else would fit in that space. And it's not just that one port; there are four symmetric ports with exactly the same problem (the pictures show two of them). I don't know much about vacuum chamber design, but it seems to me that they could have been moved just a few degrees around the chamber to avoid this problem altogether.

On the other hand, the plate will be suspended under the lower electrode anyway, and wouldn't be able to move above it anyway. In fact, the lower position for the rod is probably better, since a smaller distance from rod to plate will diminish the effects of swinging, not to mention that it will be much easier to attach when working through the front window. Not only that, but we couldn't find any Wilson seals (that's the thing the rod is passing through in the left picture, that allows it to turn while sealed) that would fit the small mini-conflats at the top; we'd need an adapter from normal-size down to mini, and we couldn't find enough of those either. The lower holes are the normal size (2⅛''), which is the standard size for our Wilson seals. Now that I think about it, there's really no benefit of using the top ports in the first place. That doesn't make me any less annoyed by the four nearly-useless ports, but maybe it was for the best.

Anyway, the rod we got was much more flexible that I would like, but it would have worked if we could machine it. Oh well. You can see that the rod is bending upwards from the force of the electrode in the second picture; we should be able to minimize that bending with the more rigid plastic and the grooves we will cut for the electrode. Despite the bending, though, our rod turned smoothly. I was also worried that plastic wouldn't maintain as good a vacuum through the Wilson seal, but it seems to be working.

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In other news, I went to a seminar today; it was a powerpoint presentation about how to give powerpoint presentations, so the presenter quite rightly skipped through it quickly and instead spent the time showing off the project her high-school intern was working on (and had been for a year prior to that). It was an air-plasma dialectric barrier discharge device; put more simply, it formed plasma arcs between your finger and the electrode when you were nearly touching it, thanks to some nifty voltage pulsing and a dialectric insulator between your finger and the high-voltage inner electrode. One of the interesting elements was that it formed in air (you could see the purple glowing arcs on your finger, and hear the buzzing from the many arcs); normally we work with low-pressure plasmas, since it's much easier to get arcing when there are fewer molecules to get in the way (hence why lightning, an air plasma, needs such a high current to form). The tricky thing is forming plasma at both a high pressure and a low current. The technology itself has lots of interesting applications, particularly with its interaction with organic matter. The presenter talked about the fact that the arcs sterilized whatever skin it was arcing to, and the intern's main research goal was to confirm that it could be used to apply a coat of cells to something, as in skin transplants and the like.

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I've also finally started my paper. I'm still not sure what the focus of my paper will be; it's either "here's how to generate a shock", or, "here's three ways how to not generate a shock", depending on the results, but of course a lot of it overlaps, so that's what I'm working on.