Plasmas!

These next few posts will be fairly technical in nature, though I'll do my best to not seep them with jargon. However there will be several posts (I've already got them in my head!) that will be chock full of jargon and these will be mainly for my physics friends back home.

I'm going to talk a bit about plasmas, the 4th state of matter. The ions that we're studying are created in plasmas (Ar-36 plasmas, to be exact) and these plasmas are controlled via magnetic fields. Obviously, it seemed to behoove me to understand them at least on a conceptual level. We're all familiar with the solid, liquid, and gas phases of matter. The plasma phase of matter is most closely related to the gas phase in that a plasma is a partially ionized gas. If you reach back to high school chemistry (a disgusting time, I know) you'll recall that an ion is an atom that has an electric charge either by stripping it of one or more electrons (giving it a positive charge) or by adding one or more electrons (giving it a positive charge). Depending on the field of science/engineering that you're working in, a "plasma" could need to be fully ionized (all the atoms are ionized) simply fractionally ionized. I'm not sure on what the True Physics Definition (TM) is, but that's really not important.

How are plasmas created? I'm not sure in general, but I know how we create our Ar-36 plasma: by applying a potential difference between the two surfaces between which the gas inhibits and causing an electric discharge from one surface to the next. In essence, we shock the shit out of it. By giving the gas atoms enough energy, electrons are stripped off the atoms. Where these electrons go and what happens to the ions is what makes plasmas so special. We now have this plum model picture of 3 things floating about: Neutral atoms, positively charge ions, and electrons (the ones stripped from the neutrals). One thing that's awesome about electrically charged things is that we can control them with a magnetic field. By applying a magnetic field with the right geometry and magnitude we can cause the plasma to flow around it's container in a nice, orderly fashion.

This flow has distinct, separate layers. Since the electrons have much lower mass than the ions/neutrals, they flow on the outer most layer (called the plasma boundary) while the ions and neutrals flow within this boundary. Now, due to conservation of charge, the plasma as a whole is electrically neutral, but that doesn't hold true for its constituent parts. With the electrons on the outside and the positive ions on the inside, a potential difference is created. This potential difference is what keeps the inner section inside the barrier. Imagine marbles rolling around in a bowl. To escape the bowl, you'd have to flick them, roll them, or somehow provide them with some external energy to escape the bowl; this is essentially what is happening.

I will go into why plasmas are important to my project in future posts.