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Stellarators are one of those things where the visual complexity tells some basic part of my brain that 'this can't be the real thing'. Simplicity bias, I guess
by doctorhandshake 3y ago
Stellarators are one of those things where the visual complexity tells some basic part of my brain that 'this can't be the real thing'. Simplicity bias, I guess.
- phkx 3y agoYou can get a free guided tour at the Greifswald site of the IPP in the north of Germany to convince yourself of the physical reality. https://www.ipp.mpg.de/visitors https://www.ipp.mpg.de/visitors
- doctorhandshake 3y agoMan that sounds cool. To clarify, I meant “that looks too complex to be the ‘right’ answer”.
- deleted 3y ago[deleted]
- phkx 3y agoGot it. Yeah, some intuition would make you think that the problem is somehow symmetrical, since other electromagnetic systems don’t have this ‚organic‘ kind of shape.
- pgeorgi 3y agoSymmetrical except for gravity that always points downwards. I wonder if it's easier to pull off fusion in a (close to) zero gravity environment because the plasma doesn't budge by other effects than the container's.
- doctorhandshake 3y agoI can only imagine taking one factor out can’t hurt
- itishappy 3y agoIt is, it's just rotational instead of mirror symmetry. Check out some of the images further down this page: https://en.wikipedia.org/wiki/Stellarator https://en.wikipedia.org/wiki/Stellarator My understanding is that the different sections of the torus experience different forces (inside vs outside due to the varying radii, top vs bottom due to gravity), which the Stellarator design attempts to compensate for by twisting the plasma so that no particular clump spends all of it's time in the same section. > The basic concept was a way to modify the torus layout so that it addressed Fermi's concerns though the device's geometry. By twisting one end of the torus compared to the other, forming a figure-8 layout instead of a circle, the magnetic lines no longer travelled around the tube at a constant radius, instead they moved closer and further from the torus' center. A particle orbiting these lines would find itself constantly moving in and out across the minor axis of the torus. The drift upward while it travelled through one section of the reactor would be reversed after half an orbit and it would drift downward again. The cancellation was not perfect, but it appeared this would so greatly reduce the net drift rates that the fuel would remain trapped long enough to heat it to the required temperatures.
- mpweiher 3y agoThe thing is: the complexity of the device translates into simplicity of the plasma. And vice versa. Tokamaks are nigh impossible to control. Stellarators, if you can build them, just hum along. And Wendelstein-7X proved that, though tricky, we can build them. Oh, and that the humming-along part is actually true. Last I checked, the maximum time for a Tokamak is 30s so far, Wendelstein has already achieved 8 minutes and they're shooting for 30 minutes.
- namuol 3y agoWhat’s the big trade off then? As I understand it there’s more funding in tokamak research.
- mpweiher 3y agoAs I wrote: the tradeoff is the complexity of the device. I once listened to a fairly long podcast on the history of Wendelstein-7X, and apparently the mathematical/computational modelling required to figure out a decently optimized stellarator simply couldn't be done when the first ones were built, so they were very inefficient and easily beaten by the Tokamaks, and so interest and funding understandably shifted. That changed when compute became much cheaper, and apparently some researchers created software models that they could run on their PCs and the late 80s, maybe early 90s. This was largely ignored for quite a while, as all the focus was on Tokamaks, for example JET and later ITER. Having cracked what to build, and somehow gotten funding, the problem was then actually building it. Very, very challenging, and it did take a lot longer to build than even initially planned, and it wasn't clear that they would succeed in building it. But they did. And ever since then, it's been humming along nicely.
- pests 3y agoThis might be a clue from Wikipedia - The release of information on the USSR's [better performing] tokamak design in 1968 indicated a leap in performance. After great debate within the US industry, PPPL converted the Model C stellarator to the Symmetrical Tokamak (ST) as a way to confirm or deny these results. ST confirmed them, and large-scale work on the stellarator concept ended in the US as the tokamak got most of the attention for the next two decades.
- mousetree 3y agoHave you visited? Recommend? This looks very interesting. I think I might take a drive up there sometime.
- phkx 3y agoI haven’t been there, yet. A friend recommended it, though. Besides a look at the machine, there seem to be a bunch of stories about things they had to solve along the way to build it, e.g. to achieve the precise 3D positioning of the parts.
- HPsquared 3y agoI get that feeling looking at CPU die images.
- adhesive_wombat 3y agoEspecially when you consider that the image is a top-down view of dozens of layers and contains billions of connections. Amazing it works at all. And then consider it can be yours for something on the order of between an hour's and a day's income. Or, for one a few years old, practically free.
- tnecniv 3y agoIt’s a trade off. Crazy geometry to try and make the physics of the plasma less crazy. At least that’s my understanding from my friends who study plasma physics
- doctorhandshake 3y agoYeah it almost looks like something where the geometry is the result of trial and error rather than first principles design. Like ‘whoops hit the side again lemme put a magnet there’ x 10e4
- rcxdude 3y agoThat is basically what it is: it's the result of running an optimisation algorithm.
- Tade0 3y agoWhen I first saw a picture of the Wendelstein 7-X I could not make sense of it - it was really like some kind of alien artifact. And when you think what it actually does then 50 years ago, back when they were merely a concept, it could have passed as one.
- scotty79 3y agoI think humans have very limited capacity for reconstruction of 3d object from 2d image for anything beyond basic shapes or something they encountered extensively in real world. Viewing 3d model of 7-X might be easier to comprehend.
- phkx 3y agoQuickly skimming over the links from your profile, I‘m surprised that the non-reality of things might be a challenge to your brain. Cool stuff, will check it out more deeply.
- doctorhandshake 3y agoHa yeah nothing approaching the mind-shattering complexity that produces something as alien looking as a captured and suspended donut of sun-stuff.
- Syzygies 3y agoHow about the visual complexity of the coronavirus? Of course, you could challenge its effectiveness, too. London ended its cholera epidemic by no longer drinking sewer water. We still don't vent our buildings properly.
- creer 3y agoElegance is an engineering trope. But perhaps by now, it's just convenient. Engineering has gotten very good at managing complexity. See production machines like stealth fighters, relay-and-rotor-age pinball machines, military submarines, navigation or gunnery mechanical calculators, large construction projects... Some generations of CPUs are elegant in their return to first principles while others throw in everything but the kitchen sink in an unholy mess; Mainframe manufacturing is a gorgeous history of containing and organizing chaos. Fusion research machines are very complex, yes, but by this point... it's only so much of an obstacle. We might be tempted to throw in software ... Eh, perhaps we are not all that good with that yet. I mean, plenty of complexity, but not yet all that much "managed complexity".
- api 3y agoWho says the stellarator isn't elegant? What I see when I look at it is something where the math is probably quite elegant. Fractals are simple mathematical expressions that generate outputs that appear to have infinite complexity.