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Just curious as to why a Mobius strip type arrangement is better than a toroid? Is it anything to do with the turbulence in the plasma flow being easier to cont
by Simon_O_Rourke 3y ago
Just curious as to why a Mobius strip type arrangement is better than a toroid? Is it anything to do with the turbulence in the plasma flow being easier to control?
- KyleBerezin 3y agoThese are great questions for someone more knowledgable, but as I understand it, If you follow a single point on the surface all the way around the loop, it will spend as much time in high confinement as it does in low confinement. That explains why folding is important, as for the mobius, I oversimplified a bit. The Wendelstein has 5 folds, making it a mobius, but I think I read about one in Spain that had only 4 folds. That would mean the mobius isn't imperitive, but I'm sure there is a good reason for it. Really a stellerator doesn't need 'folding' at all, they can be as simple as a twisted torroid. I didn't want to go into excruciating detail though, the more in detail I go the more likely I am to say something that is wrong lol. Edit: I looked it up, the one in spain is called "TJ-II"
- NovaDudely 3y agoFirst thing that comes to mind is like twisted pairing on cables. Distributes the external/internal forces more equally. Is it anything like this?
- KyleBerezin 3y agoNo, twisted pair wires are really cool but different. When you push current down one wire you pull current down the other. The signal is passed through the differential of those 2 wires. If the wire is hit with EM interference, that change will be seen as a 'common mode voltage', that is, both wires will be 'pushed' or 'pulled' the same amount, and you won't see a differential. That effect works both ways too, where a single wire with a digital signal will spew out radio waves, 2 wires with opposing signal cancel each other out and emit no em waves. The effect with the stellarator is more like stirring a pot.
- NovaDudely 3y agoThank you for the clear explanation! I love it!
- Bjartr 3y agoI think it's about ensuring the plasma heat/energy distribution is more uniform so you get fewer outlier particles with high enough energy to escape confinement and damage the interior of the reactor. Or something like that.
- extrapickles 3y agoIt primarily has to do with the physical construction of the magnets, in a toroid the inside of the toroid effectively has more windings per meter of circumference than the outside causing uneven containment. With mobius strip you regularly flip between inside and outside, so the plasma particles get more even force applied.
- cyberax 3y agoIt's actually really easy to explain. Draw a torus and then draw rectangular "bands" across it, they will represent the containment magnets. Due to pure geometry, the area closer to the center will have a smaller distance between bars. This means that the magnetic field will be stronger near the center. This in turn means that particles will separate (depending on charge) and drift to the sides. It seriously interferes with the containment. You can fix that by changing the torus into something resembling "8", so that particles move to one side when they fly through the upper part, but then they'll move back as they fly through the lower part. Of course, you can't just do that in 2D because the part in the middle of "8" will have no magnetic field. You need something without self-intersections. You can try to move one side up and another down. But that doesn't quite work either because you will get another set of preferred directions. So instead you go with the gentle twisting, resulting in the Möbius-looking shape.