[HN Gopher] Wendelstein 7-X: Gigajoule energy turnover generated... ___________________________________________________________________ Wendelstein 7-X: Gigajoule energy turnover generated for eight minutes Author : greesil Score : 274 points Date : 2023-08-11 18:36 UTC (4 hours ago) (HTM) web link (www.ipp.mpg.de) (TXT) w3m dump (www.ipp.mpg.de) | YossarianFrPrez wrote: | If I understand things correctly, the problem with magnetic | confinement (e.g. Tokomaks, Stellarators) is that once you have | heated a plasma such that it is "fusing," how do you get the | power out with out cooling the very plasma you've just spent a | lot of energy heating up? | | Helion, a fusion startup, claims to have solved this problem via | capturing an induced current from colliding two hot plasmas | together. I'd be curious if there is any way the Wendelstein can | produce electricity. | Tuna-Fish wrote: | Most fusion power systems assume they are doing that as | neutrons. D-T fusion conveniently has the proportion of energy | that gets lost from the plasma as KE of neutrons be pretty | close to the amount of energy that a conveniently sized fusion | reactor can afford to remove from the plasma. | | Then you trap the neutrons with, for example, a lithium | blanket, use them to breed more tritium, and produce energy | with a turbine from the heating of the blanket. | YossarianFrPrez wrote: | Ah, got ya. Thanks for the information. | karmajunkie wrote: | This is perhaps an obvious question to some, but I'll ask it | anyway: How is the power generated here converted into usable | electricity? | | I know for conventional fission reactors the heat of fission is | basically used to run a steam turbine. Given the extreme heat of | the plasma, and that it must be magnetically suspended so that it | doesn't even touch the sides of the containment, how is that heat | transferred to some other medium to generate electricity? | mdprock wrote: | here there is no power generated as it's not working with | deuterium-tritium. most of the heating will heat the plasma and | a fraction of this will reach the cooling system. To make a | comparison ITER is expected to have 50 MW heating for 400 | seconds approx. = 20 GJoule. Using a DT mix will result though | in 500 MW Fusion Power | peteradio wrote: | You still get heat transfer from uncharged elements I guess. | Etheryte wrote: | I'm not sure if it's the case for this specific reactor, but | the common answer to this question is that you need cooling in | the surrounding walls and the coolant that runs through the | walls transfers the heat out where it can be used to do useful | work. | WJW wrote: | Given that the plasma is several million degrees, it will | radiate a lot of energy and heat up the walls even if it does | not directly touch them. Just cooling the walls can heat up the | cooling fluid enough to later produce steam with. AFAIK the | Wendelstein machine is not configured for electricity | production though, so the cooling is just cooling atm. | jeffbee wrote: | > Given that the plasma is several million degrees, it will | radiate a lot of energy | | That doesn't entirely follow. 2 particles whizzing past each | other at relativistic speeds have extreme temperatures but | don't offer much energy. Mass is in this equation. | willis936 wrote: | What if you have 10^20 particles? Each charged particle | emits photons with energy/frequency proportional to their | speed (Bremsstrahlung). This is mostly from electrons | because they are much lighter and so are much | hotter/faster. Plasmas are quasineutral though so you'll | have those electrons present. There is a long line of | research trying to get away from that constraint with | little luck so far (but it should continue to be worked | on!). | | Jumpjng back up the stack: photon radiation is mostly | considered a loss since it transfers energy out of | confinement and does not impart it on other fuel. You | nominally extract your heat via neutrons: same as fission | reactors. Some designs (Helion) aim for reactions with | charged byproducts. The reaction produces a current that | can be coupled by a surrounding coil, much like a | transformer but powered by current induced by plasma rather | than another copper wire. | fizigura wrote: | They currently run a bad-ass heatsink (which is one of the main | challenges of this project, i.e., how to cool it), but | eventually you will use that heat to convert it into | electricity, yes. | | For the German-speaking crowd here, the Alternativlos podcast | guys were there twice and had lengtly conversations with the | researchers there. Like, between nerds. Really cool, if you | understand the language. | | https://alternativlos.org/36/ (from 2016) | | https://alternativlos.org/51/ (most recent, from may 2023) | drannex wrote: | Omega Tau also visited and talked with some of the | researchers and has a great podcast episode on it (and truth | be told, all of their episodes are great). | | https://omegataupodcast.net/312-the- | wendelstein-7-x-fusion-e... (from 2019, 3Hrs, English) | tsimionescu wrote: | Most of the answers are missing the actual (proposed) | mechanism. | | The energy of the reaction is mostly carried away as high- | energy neutrons. So, the way to get energy back is to "capture" | those neutrons. Since neutrons are not electrically charged, | you can't use them to directly create electricity, so all | you're left with is using them for heat. | | Unfortunately, since they are electrically neutral, they're | also relatively hard to catch. You need a dense material where | they will have a good chance to hit some nucleus. The proposed | designs are typically some kind of liquid metal blanket being | circulated around the reactor and onto a place where it can | boil water to produce steam to spin a turbine. Lithium is the | metal most proposed for this, since it also has the advantage | that it can produce tritium when bombarded with neutrons | (tritium being the super rare half of the fuel that goes into | the reaction). | nerdponx wrote: | It's always fascinating to me that, no matter how many | interesting new ways to release lots of energy we develop, we | are still stuck with the same method for converting it to | electricity: release the energy as heat, use heat to make | steam, use steam to drive generator. | jessriedel wrote: | The reason just that this is a simple process for which a | steam turbine can achieves 90% of the thermodynamic | optimum. To my knowledge, the only reason people consider | alternatives is to reduce capital costs. You're still | capped by thermodynamics though. | sambapa wrote: | It's because we're in local maximum - steam turbines are | just so developed | NateEag wrote: | Helion is planning to use induction to generate electricity | from the fusion reaction's generated magnetic field, IIUC: | | https://www.helionenergy.com/faq/ | | (See "How does Helion generate electricity from fusion?" | question) | MichaelZuo wrote: | Which doesn't make sense for power generation since there | will always be some percentage of neutrons produced by | any type of fusion reaction that can only be useful for | generating steam. | | To entirely skip the steam cycle portion is to | intentionally make a much less efficient design. | | For space-constrained, high-value, applications where | economics don't matter that much, such as a submarine, | that would make sense, but otherwise... | jessriedel wrote: | You could always add the liquid metal blanket if you want | to eke out the extra 10% (or if you want to generate | tritium). But it's not worth the complication in an early | prototype. | gus_massa wrote: | They plan to use 2D + 3He -> 4He + 1H, so no neutrons htt | ps://en.wikipedia.org/wiki/Aneutronic_fusion#Candidate_re | ... | | (I'm still not convinced of their explanations, but a | fast proton may be easy to catch by the magnetic field | and create the effect they want.) | 2-718-281-828 wrote: | probably boiling water and the steam drives turbines whose | coils and rotating magnets produce electricity. | idiotsecant wrote: | Yes, the boring and actually feasible answer is steam. | | But it sure is fun to dream! | | https://en.wikipedia.org/wiki/Direct_energy_conversion | midasuni wrote: | Isn't one of the problems with nuclear that it increases | water temperature in rivers | calfuris wrote: | That's a problem associated with a particular cooling | system design, so it's more of a thermal power problem than | a nuclear power problem. | jtriangle wrote: | Same way most electricity is made, you use the energy created | to heat up water into high pressure steam, high pressure steam | turns a turbine(s) which turn gensets that produce 3 phase AC | current. | | This one in particular isn't setup to do that, and as far as I | know, none are yet. It's a pretty simple engineering problem, | and, until we can maintain fusion for months at a time, it's | not really something that needs to be built. | | There is, however, one fusion concept that shows some promise | that doesn't require all that that helion energy is developing | (helionenergy.com) they're yet to create net-power, but, their | idea has some promise, and avoids the common problems with | other forms of fusion power. I don't really see it as the be- | all to end-all in the space, but from what I can tell they very | well might be the stopgap that is needed between large scale | stellerators and fission. | mjfl wrote: | The Stellarator is theoretically a superior design over the | Tokamak, designed to neutralize the JxB force, where J is the | current through the plasma and B is the magnetic field guiding | the plasma around the device. By twisting the plasma into a shape | where the curl of B (proportional to J) is parallel to B, i.e. a | helix, the cross product is 0, and thus there are no net | magnetohydrodynamic forces on the plasma. | juujian wrote: | 'Theoretically' is the right word for sure. iirc, the | predecessor of the Wendelstein led to the bankruptcy of the | engineering firms building the parts, because tolerances were | so tight and they failed multiple times to land within the | constraints. | mjfl wrote: | true. but on the other hand, the 'theoretical' is being | turned into practice as evidenced by this 8 minute | containment. the best a tokamak can do is half a second. | moffkalast wrote: | The last time it was in the news I think naysayers listed the | main caveat with stellerators as something along the lines of | very low plasma density compared to tokamaks, which makes them | unable to get anywhere close to the energy break even point. | expertentipp wrote: | With gas cut off from pipeline terminated in Greifswald, how will | they power now this bottomless energy pit? They still have some | money, but a finite amount. | TaylorAlexander wrote: | Speaking of fusion does anyone know what is going on with SPARC | at Commonwealth Fusion Systems? I have been very excited about | their system but they are understandably in a deep development | and construction cycle after a $2B investment, so all their news | page has for the last year are updated business deals and awards. | I would love to hear how reactor construction is going. | cmplxconjugate wrote: | My best friend works for them in diagnostic sub-systems | development. The product is still a long way off delivery with | many systems being actively designed and refined. Basically | it's busy but will still be quite a while (3-5+ years at | least). | TaylorAlexander wrote: | Makes sense. I would love to see a blog post with some | progress pics, but I understand that building a fusion | reactor is simply a slow process! | [deleted] | aidenn0 wrote: | What is "energy turnover" in this usage? | | [edit] | | Found it: "Energy turnover is defined as the amount of heat | multiplied by the duration of the discharge[1]." By "amount of | heat" I assume they mean "heating power delivered to the plasma" | b/c the the only way to multiply by time and get Joules is to | start with power. | | 1: | https://gigazine.net/gsc_news/en/20230227-wendelstein-7-x-en... | snarkconjecture wrote: | Yes, it's a little buried but the article says | | > The energy turnover results from the coupled heating power | multiplied by the duration of the discharge | | The numbers: | | > The energy turnover of 1.3 gigajoule was achieved with an | average heating power of 2.7 megawatts, whereby the discharge | lasted 480 seconds | | Also: | | > Within a few years, the plan is to increase the energy | turnover at Wendelstein 7-X to 18 gigajoules, with the plasma | then being kept stable for half an hour | | i.e. 10 megawatts for 30 minutes | magicalhippo wrote: | How long does it take to restart after losing stability? | | Ie, would it be feasible in a power plant scenario to settle | for 30-60 minutes of stability, and just restart? | amelius wrote: | Isn't this similar to the monetary meaning of the word | turnover? Like turnover : profit <==> energy turnover : net | energy output? | runako wrote: | Possibly the poster is from a country like America where | "turnover" is not a preferred term to refer to gross receipts | of a business. (Americans typically use "revenue" instead.) | aidenn0 wrote: | I am indeed from the US and had never heard "turnover" to | mean gross receipts. | alkonaut wrote: | So when this had a turnover of 1.3 GJ (361 kWh), was that | with a net loss in the end? How much electricity did they put | in? | aidenn0 wrote: | My layman's understanding: | | There has never been a net-positive-energy magnetic | confinement fusion experiment. Inertial confinement fusion | has had 2 events that were "more energy out of the fuel | than delivered to the fuel." But is still about a factor of | 100 away from what is needed for "more electricity in than | out" | [deleted] | fefe23 wrote: | FYI: This milestone was in February. | ChuckMcM wrote: | I love these guys, they are just knocking down the engineering | challenges in their plan to completely characterize and control a | fusion stream. Sometimes they feel like the Tortoise in the race | to a working fusion power plant but they are answering questions | (managing wall temps and hold fusion in streams[1]) that the | Tokamak folks have yet to solve. My bias though is I'm way more | on the "D" side of the R&D spectrum and following ITER often | feels like pure "R." | | [1] https://www.iter.org/of-interest/1188 | aquafox wrote: | Interesting fact: Nuclear fusion, even if we'll make it work, | won't stop global warming, because the heat it creates heats up | the earth enough to bring us outside the Paris agreement: | https://twitter.com/rahmstorf/status/1605967891928596481 | RivieraKid wrote: | One immediately apparent flaw of this argument is the | assumption of energy use growing by 10x over a century. But in | developed countries, energy use per capita has been roughly | stable for decades. The 2 main drivers of energy growth will | weaken over time (population growth + countries becoming | developed). | | Also, if energy use does increase by 10x, the solution is | simple, build giant refrigerators powered by fusion energy to | cool the atmosphere. (joke) | MichaelZuo wrote: | I could see a plausible 10x growth if literally the entire | world achieved within the ballpark of 2023 US levels of per | capita wealth. | andbberger wrote: | this is a basic consequence of thermodynamics and true for all | power generation. the only thing to be done to minimize waste | heat is to to increase temperature of the hot side of the heat | engine, with ie advanced fission reactors. | | and fusion never had any advantage over fission anyways, other | than that people aren't scared of it yet. | aquafox wrote: | Why the down votes? What is factually wrong with that | statement? | constantcrying wrote: | The threat of the earth heating up by 0.3 degrees due to | energy production is irrelevant or at least absolutely worth | it as a tradeoff for working fusion. | | The dangers of climate change is not that the earth heats up | by some small amount, the earth can easily cope with that. It | is that continued greenhouse gas emissons are causing a ever | increasing heatup due to trapped solar energy. | | (It is also extremely strage that he argues for geothermal in | his comments. Does he not realize what that is? Literally | heating up the surface of the earth with energy from below.) | coolspot wrote: | Didn't downvote you, but having unlimited energy source is | worth it and can allow us to remove heat from earth. Human- | caused CO2 alone contributes 2.1W/sqm while all current human | energy production is 0.04W/sqm . Removing extra CO2 alone | would offset 50x energy production growth. Then you can do | things like placing reflective satellites between earth and | sun. | pfdietz wrote: | Because the argument involves unlimited future growth in | energy use. Compared to the current energy use, fusion | (assuming it could be made to work practically) would indeed | solve global warming. | EVa5I7bHFq9mnYK wrote: | The burning of 1 kg of coal heats the earth in two ways: | | A) the energy that is produced immediately (about 24MJ) | | B) the excess energy absorbed from the Sun over many | subsequent years, caused by CO2 emitted burning that coal. | | The B is much larger than A. The fusion only produces A, but | not B. | slashdev wrote: | Assuming I trust the math, that's plotting exponential growth | in energy usage out for 80 years, and assuming a fully nuclear | grid. Neither of those is likely. Lastly the Paris accord is a | pipe dream that will never happen. A target to aim for, and | miss. Nothing more. | lhoff wrote: | Related recommendation for the german-speaking crowd here: | | The Podcast Alternativlos by Felix Von Leitner and Frank Rieger | were twice in Greifswald to interview some of the people behind | the Wendelstein. In the first episode | (http://alternativlos.org/36 from 2016) they mainly focused on | the development and build process and the history. The second one | is from this year and they talk about the achievements and the | future of Fusion (http://alternativlos.org/51/) | anonuser123456 wrote: | I don't get it; who cares? We know the equations to burn plasma; | that's the easy part. | | The hard part is building a machine that can burn plasma and | breed tritium at appreciable rates. | | Why even bother with these machines that can never be built | economically? | constantcrying wrote: | >Why even bother with these machines that can never be built | economically? | | If you can not build a research reactor which functions well, | then "building a machine that can burn plasma and breed tritium | at appreciable rates." is more than impossible. | fizigura wrote: | We know the equations for flight. Why didn't they just build a | 787 in the 40s already? | | Oh, is it because the technology didn't exist and first had to | be developed, in incremental refinements? Initial airplanes | didn't even fly and half the people trying them died? Oh... | munchler wrote: | Maintaining a controlled fusion reaction for eight freaking | minutes seems like a pretty worthwhile accomplishment in and of | itself. The only other place this is known to occur is in the | center of a star. Doing it here on Earth is pretty mind-blowing | IMHO. | foolfoolz wrote: | i've been following this project for 10 years. it's been | successful. but how do projects like these move faster? the | wendelstein 7x is never going to generate usable electricity. | it's supposed to be the pre cursor to the producing reactor | barbazoo wrote: | > the wendelstein 7x is never going to generate usable | electricity | | What's the reason for that? | AnimalMuppet wrote: | It's a research reactor, not a production reactor. Generating | useful electricity was never the design goal. The goal was to | learn _how_ to build a reactor that could generate useful | electricity. | ethbr0 wrote: | tl;dr - Output nuclear fusion power, plasma volume, and | magnetic field strength scale differently with reactor size | increases | | In detail, I'll let someone smarter than me in nuclear | physics explain: https://physics.stackexchange.com/questions/ | 175830/nuclear-f... | KyleBerezin wrote: | We are researching fusion technology. It would take a reactor | many times larger to get more energy out of the facility than | you put in. The technology still needs to mature before a | reactor that size would be financially responsible. | aeyes wrote: | In the German Alternativlos podcast the Wendelstein team | (Prof. Dr. Thomas Klinger, Dr. Adrian von Stechow) recently | stated that it is already feasible, they estimate a cost of | ~EUR20B and a 5 year construction time for a commercial | fusion power plant if we started now. | | https://alternativlos.org/51/ | KyleBerezin wrote: | Yea, but compare the financial burden of that compared to | a solar farm of the same output. Not to mention the | technical risk. | fizigura wrote: | Solar farms on farmland? That won't scale to the energy | needs of 8bn+ people if we still want to keep feeding | them. Especially a non-vegetarian diet. | KyleBerezin wrote: | I'm just saying the money doesn't back the idea yet. I'm | not anti-fusion. | bmicraft wrote: | No, solar farms in the desert with a HVDC lines | obviously. | t0mas88 wrote: | For less than 15 billion euro you could buy enough solar | to power a country the size of the Netherlands. With 5 | billion to spend on batteries you might even make it | through night time usage. | | Or in other words: Fusion is too expensive at this point | to be useful. | jahnu wrote: | That seems amazingly cheap! Are we really down to that | low level of cost? | sp332 wrote: | Grid-scale solar is $33/MWh (+) | https://emp.lbl.gov/publications/utility-scale- | solar-2022-ed... and the Netherlands uses 1,000,000,000 | MWh/year | https://ourworldindata.org/energy/country/netherlands so | it's only off by a factor of ~2. | | (+) These numbers are for the USA. I found a mention of a | cheaper project in Chile | https://about.bnef.com/blog/cost-of-new-renewables- | temporari... but I don't know what the situation is in | Europe. And wind might be even lower. | aeyes wrote: | Chile is an outlier, the plants are in remote locations | in the Atacama desert where you have two compelling | reasons to build solar plants: There is a lot of space | where nobody lives and the sun is always shining. There | are mountains but there are also lots of places which are | flat for as far as the eye can see, an example would be | the Cerro Dominador plant which probably didn't require | any ground preparation. | | On http://generadoras.cl/tipos-energia/energia-solar | scroll down to "Capacidad por region", Antofagasta and | Atacama are the desert regions in the with over 90% of | installed capacity. | | In Germany or the Netherlands it is a bit harder to find | space for large solar plants. | bbarnett wrote: | The first plant is going to be more expensive, and the | next gens after that will benefit from things learned. | | The first TVs were for the very rich, and had 4" bw | screens. Now they're 80", thin, and insanely cheap. | peteradio wrote: | How exactly is that calculated? | fizigura wrote: | The same was said 20 years ago about solar power. | | Then some countries stepped up the subsidies game and | booom, prices fell dramatically since suddenly everybody | wanted a piece of the cake. And competition drove this | all down. | | All you need is for somebody to start. Or we just keep | telling ourselves that it's too expensive, shrug, and | move on. | | Also note how the goal posts changed. Until recently, | everybody made fun of fusion by basically saying it's too | hard, it's too far in the future. Now it's not too hard | anymore, it's just too expensive. What's next? Too loud? | Too big? Induces headaches with the esoterically minded? | cyberax wrote: | You'll freeze to death in winter, but that's a minor | thing. Living is overrated. | jasonwatkinspdx wrote: | You can't jump from idea to production power plant in one | step. This is research about the fundamental science | involved. What they're doing is incredibly difficult and | complex. They have a plasma at millions of degrees mere | centimeters from superconductors at near absolute zero. The | field geometry and interactions are so complex it brings even | current supercomputers to their knees. The device wasn't even | possible to simulate until the late 90s using the biggest | machines in the world. | | What they've already demonstrated is a tremendous | accomplishment. But apparently if it doesn't go from idea to | an option in door dash in 6 months flat that's not good | enough for people here. | constantcrying wrote: | >What's the reason for that? | | It is about research. It generating usable electricity is | absolutely irrelevant. | | You need research projects to figure out what works and what | doesn't. The goal isn't to build a practical reactor. | Eji1700 wrote: | Mostly, they don't? | | There should be more funding in this area, but at some point | you've got to build it, and that takes a ton of time. | Regulations/bureaucracy could be better but at the end of the | day you're not going to cut off a ton of time safely. | | Once you have a working model iteration gets much much faster, | but we've simply been hitting walls for decades. | hedora wrote: | Is there a minimum viable size for a fusion reactor? If it | scaled down ennough, they could just launch prototypes into | space, and see if they explode. | adhesive_wombat wrote: | Fusion reactors are pretty non-explodey. Really all they | can do is spring a leak, then fill with air and extinguish | the plasma. Maybe if you quench the magnets hard enough you | might get something dramatic like leaking a gram of | tritium. | b3orn wrote: | I'm no expert on this, but a minimum viable size exists and | it's much larger than what you could just launch into | space. I watched a video on this years ago, I don't recall | the exact relation to size but if I'm not remembering this | completely wrong there's a minimum size you need for a | fusion reactor to "ignite", ITER is huge for a reason. | willis936 wrote: | ITER is huge because it uses weak magnets. | Eji1700 wrote: | I'm honestly not sure if you're joking but in case you're | not, the "minimum viable size" is hardly the largest issue | with what you're proposing and it sounds like you're not | getting what the key issues are. | | You're talking about taking a technology that's so finicky | we've barely gotten it to work after almost 100 years and | rocketing it into space? We're no where near good enough at | this to get a test that would work after the extreme | violence of an escape velocity launch. | | Further fusion reactors aren't like fission. "exploding" | really isn't a problem . Keeping the reaction going in an | efficient manner is. | | IF exploding was a problem, space is probably the worst | place for it? Putting it way underground would be vastly | easier and a hell of a lot safer because you won't have | material possible falling back to earth/hitting satellites | in orbit. | sdwr wrote: | That was not a real question, it was a subconscious plea | for elon musk to take over and make it work. | | "Shooting it into space" is a reference to how SpaceX | disrupted the rocket industry through a "fail fast" | mentality, aggressive goals, and sheer force of will. | flotwig wrote: | Please don't "move fast and break things" with nuclear | fusion :-) | Eji1700 wrote: | This take is even more baffling to me than the original | question. | ladams wrote: | Stellarators in particular suffer from very long development | cycles. It takes years and years of research to develop the | algorithms used to optimize the coil geometries, and then the | production of the coils and assembly of the vacuum vessel | within the coils is much more challenging than for a tokamak. | The coils are hard to produce because they have highly | irregular shapes, and tight tolerances. Assembling the vacuum | vessel is hard because the coils cover much more of the | "toroidal-ish" surface area than in a tokamak. | | The is a lot of interesting work going on in stellarator design | optimization now, but it will likely be many years before that | research is realized in another actual reactor. | fizigura wrote: | For a few billion USD you could build a real power plant of | this type. Sounds expensive, but consider how much money | nuclear fission did cost initially, and how much money we | burn on other stuff, then it's not unthinkable to have | somebody rich chip in and make it happen. (Germany just gave | $10bn subsidies for a domestic Intel factory.) | Guvante wrote: | They managed to handle what a fission reactor outputs every | second in this experiment. | | I don't think that points to a commercial reactor whenever | someone spends a few billions. | willis936 wrote: | HSX beat them to the punch by over a decade. Small is easy. | Unfortunately no machine worth making (power generator | relevant) is small. Practice helps. | stjohnswarts wrote: | Can someone tell me why this won't produce commercial level | fusion for 30 years so I can shut down my eternally optimistic | "physics kid" portion of my brain for a while? | bmicraft wrote: | It will cost too much | Dulat_Akan wrote: | I am thinking why companies making so huge reactors, everything | should be simple just for test to get energy | sp332 wrote: | It's a been a long time, but in a talk at Google, I think | Bussard said that power output scales with the 5th power of the | radius of the device. There's really no point making a small | one. | pfdietz wrote: | Bussard's last reactor concept, polywell, didn't work. | sp332 wrote: | Oh right, I had WB-7 confused with Wendelstein 7. | pfdietz wrote: | I greet W7-X with a huge yawn. A reactor based on stellarators | will still be very large and have very low volumetric power | density. The beta is not good, so these would only work with DT, | and suffer from the generic problems of all DT schemes. | moffkalast wrote: | What makes tokamaks so much better at power density? After all | it's the exact same setup, just shaped differently and without | the center coil? | pfdietz wrote: | I didn't say that. Both tokamaks and stellarators on DT will | have lousy volumetric power density. Indeed, any DT scheme | will suffer in that respect. | KyleBerezin wrote: | Ahh, Wendelstein is that stellerator reactor. The stellerator is | really cool, and an alternative to a tokamak reactor. Tokamak is | the doughnut shaped reactor, and it has a problem where the | plasma near the outer circumference has less magnetic | confinement. The stellerator is similar, but confines the plasma | to a ribbon and folds it over on itself in a mobius-like | arrangement. | | I used to be really interested in this, but forgot it existed | over the years. Glad to see it works! | | https://en.wikipedia.org/wiki/Stellarator | lostlogin wrote: | Are you able to say more about what you do? Judging by your | comments, you have some idea what you are talking about. | Simon_O_Rourke wrote: | 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 wrote: | These 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" | Bjartr wrote: | I 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 wrote: | It 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. | tw061023 wrote: | What's interesting is that stellarator actually is not just an | alternative, but a wholly parallel branch of evolution - it's | not like one was invented strictly after another, and the | authors of both designs never knew about the other's work | before they completed theirs. | | What's even more interesting is that the fusor - the simplest | possible design for a thermonuclear reactor, so simple that | anyone skilled in electrical engineering and having access to | proper civilan equipment can build one with ease - seems to be | invented _after_ both stellarator and tokamak. | | That said, I never particularly liked stellarator design. The | very _complexity_ of it somehow feels subtly wrong, like | doubling down in the wrong direction. | | However, this is one of the cases where I would absolutely love | to be proven wrong. We are far past due big breakthroughs in | the field. | jcheng wrote: | > The very _complexity_ of it somehow feels subtly wrong, | like doubling down in the wrong direction. | | This made me think of modern jet fighters being designed to | be aerodynamically unstable, making them all but impossible | for human pilots to operate without flight computers. | Apparently the maneuverability benefits make the added | complexity more than worth it. | | https://en.wikipedia.org/wiki/General_Dynamics_F-16_Fighting. | .. | waterheater wrote: | Compared to a tokamak, the stellarator bring engineering | efficiency while matching performance. Though ideas for the | tokamak and the stellarator may have emerged together, the | main reason tokamaks were built first is because they COULD | be built. Without computer-assisted magnet design, | stellarators simply couldn't be properly built; the magnetic | geometries are just too complex. | | In the long run, it's not known stellarators will be the | eventual winner in the long race for a viable fusion reactor. | The attributes in a winner will be net-positive operational | efficiency and superior energy harvesting abilities. Perhaps | multiple approaches will be viable. | tw061023 wrote: | I understand the theory. I just hope I will live long | enough to see a winner in this race. | | To be honest, I've been interested in the domain for quite | a time and I still want to build a fusor or a polywell at | some point just to see it glow. Probably won't happen | though. | white_dragon88 wrote: | You know enough to say more. Say more! | waterheater wrote: | I'm not that guy, but I can speak to what you're asking. I've | followed Wendelstein 7-X for almost a decade. | | Nuclear fusion occurs at extremely-high temperatures. As you | heat your fusion fuel to sufficiently-high temperatures to | allow fusion, the matter transitions into a plasma, which is | great: plasmas react to electromagnetic fields. As such, a | major challenge with achieving viable nuclear fusion is | making a vessel capable of holding the fusion reaction. | Because we can't create on-demand gravity wells, the next | best option for confinement is using electromagnetic fields | to hold the plasma in the air. | | So, you now have an "electromagnetic bottle" capable of | suspending a fusion reaction above the reactor's walls. Now, | you have another issue: how do you ensure the fuel will | sufficiently mix to sustain a fusion reaction? One approach | is to move the plasma in a loop. The topologically-simplest | method to accomplish this loop is the torus. Such a plasma- | confinement device is called a tokamak. A tokamak uses two | magnetic fields, torodial and polodial, to accomplish its | task. The torodial field is driven through the plasma to push | it forward, while the polodial field pulls the plasma in | toward the center. Proper balance of these fields will allow | the plasma to circuit the vessel following a helical path, | achieving confinement. | | However, driving two separate magnetic fields is energy- | intensive, and a successful fusion reactor will want to | minimize its own power consumption to maximize the amount | available for external usage. Enter the stellarator. The | stellarator also drives the plasma around in a circle, it but | uses a single magnetic field. How? It "tricks" the plasma | into "thinking" there's only one magnetic field by using | computer-optimized magnets with highly-complex geometries. | This provides stellarators with a major engineering advantage | over tokamaks and is a primary reason Wendelstein 7-X would | have chosen it. | | With the confinement vessel topology largely identified, the | next main step is to figure out how to build a vessel able to | contain a sustained fusion reaction. For context, fusion | experiments traditionally only operate on timescales of | milliseconds to maybe a second. The reason? Fusion occurs at | millions of degrees, and keeping the reaction vessel cool, | ensuring a continuous supply of fuel, and dealing with | reaction "exhaust" (e.g., alpha particles) and stray high- | energy neutrons from the common deuterium-tritium reaction | (which irradiate your reactor walls because neutrons don't | react with electomagnetic fields) is a major, major | engineering challenge. Any operational, net-positive fusion | reactor must be able to operate for days, weeks, and months | on end. | | What Wendelstein 7-X has been attempting to do for years is | demonstrate that building such a vessel is even possible. | Their overall goal is to sustain a fusion reaction for about | 30 minutes. Such a timescale will show a proof-of-concept | system which enables sustained fusion reactions to occur. | | Currently, the preferred fuel is deuterium-tritium because | the fuel is generally available and has an attainable fusion | temperature. The stray neutron issue can be mitigated by | lining reactor walls with lithium to breed tritium fuel. Even | better is to use the helium3-helium3 reaction, which | completely annihilate to produce pure energy as the output | (welcome to e=mc^2, enjoy your stay). The main holdups are: | (1) the reaction occurs at much higher temperatures than | deuterium-tritium, and (2) he(lium)3 is quite scarce on | Earth. Once Wendelstein 7-X shows how to engineer a proper | confinement vessel at a "lower" temperature, you can then | work on the higher temperature levels required for he3-he3. | Also, he3 is plentiful on the surface of the moon, so mining | the surface of the moon will be performed to obtain the | required fuel, which is the fundamental premise of the movie | "Moon". | | Someone asked for information on electromagnetic plasma | containment folding. I recommend reading up on | magnetohydrodynamics (MHD). It's the mathematical and | physical foundation of your interest. | KyleBerezin wrote: | One guy asked why the mobius aspect is needed and I | couldn't answer. I know a lot of stellarators aren't odd- | period like Wendelstein, and the old designs didn't do | folding at all. Do you know what improvements the mobius | design has over something like TJ-II? | waterheater wrote: | The helical path creates a twist in the plasma which | cancels out the drift forces. This is what I meant by | "tricking" the plasma. User mjfl gives an even more | technical explanation: | | > By twisting the plasma into a shape where the curl of B | (proportional to J) is parallel to B, i.e. a helix, the | cross product is 0, and thus there are no net | magnetohydrodynamic forces on the plasma. | | Hope all that's a good answer for you. | | > Mobius aspect | | You might avoid using the word "Mobius" and instead use | "helical." A Mobius strip is important because it has two | faces which form a single surface. The surface aspect | isn't relevant in this context, so a term which refers to | the shape would likely dispel confusion in a reader. | | As far as I'm aware, each section of a stellarator is | periodic in its own right, which means the end and start | points of each section are the same. Though I'm not | certain, the choice of four versus five is more likely an | engineering factor rather than one of physics, whereas | the distinction between a tokamak and stellarator is of | physics and not just engineering. | golem14 wrote: | I suppose that any number of twists would be OK, but the | more twists, the less efficient ? | | Is that what you are saying ? Or are there other | constraints on the number of twists (e.g. must be odd, | ...) | KyleBerezin wrote: | If a 'particle' (I don't know a better word) finds itself | near one of the top divertors, at the same point in the | next orbit it will find itself near the bottom divertor. | That is a product of the "mobius-like" shape, so although | it isn't really a 'ribbon' and isn't really a mobius, it | helps explain the concept concisely. I just don't know | WHY that shape helps lol. Maybe it doesn't and it was | just a practical design change like you said. | | edit: changed language about the divertors. | gabereiser wrote: | Seconded. This is fascinating stuff and reminds me of some | crazy rant some guy was telling me about anti-gravity and how | electromagnetic "ribbons" could propel you. Obviously the guy | _was_ nuts, right? How would one go about learning more about | electromagnetic plasma containment folding? | KyleBerezin wrote: | Haha, no I am just some random guy who reads too many | Wikipedia articles. "Electromagnetic plasma containment | folding" does sound like something a crazy person at a bus | station would rant about. | | My explanation was definitely over simplified, but I'm not | knowledgable enough to go into detail on the topic. I can't | even point you towards something to read on the topic since | everything I read about it is like 15 years old at this | point. | tootie wrote: | If a Hollywood screenwriter were naming a crazy science | device, they would come up with something like | Wendelstien 7-X | tboughen wrote: | My favourite fact about it comes from | https://phys.org/news/2016-02-plasma-physicist-discusses- | wen... | | "...the supporting structure can only withstand the | forces if the interfaces between the ten individual | segments of the central rings, which weighs several | tonnes, are built with a level of precision of less than | 100 millionths of a metre..." - and they found a small | family business in the north of Italy capable of doing | this! | dale_glass wrote: | Odd units. | | 1 meter = 100 cm = 1000mm. | | So 1 millionth of a meter = 1/1000th of 1mm. | | thus, 100 millionths of a meter = 0.1mm, or ~4 thou in | American units. Easily achievable by hobbyists, let alone | by serious, professional equipment. | | Sure, that is a pretty exacting specification for what I | suppose is a big machine, but I'm pretty sure very normal | things like say, car engines get made to far tighter | tolerances. | Retric wrote: | You messed up at your last step 1 millionth = 1mm, 10 | millionth = 0.1mm, 100 millionth = 0.01mm | | 0.01mm is very difficult when you're talking large custom | objects with complex shapes. | dale_glass wrote: | Oh, English fail on my part then. I had assumed that 100 | millionths of a metre == 100 * 1/1000000. | eis wrote: | The german site of the source speaks of 0.1mm so you were | correct > bei Toleranzen von teilweise | nur 0,1 Millimeter | | https://www.ipp.mpg.de/de/aktuelles/presse/pi/2020/01_20 | starkrights wrote: | I think the original commenter is right- correct me if I | missed what you're getting at. | | Keeping it all in the same units until the end here: | | 1 millionth of 1 meter = (1 / 1,000,000)m = (1e-6m) | | 1 millionth * 100 = 100 millionths => (1e-6m) * 100 = | (1e-4m) = 100 millionths | | (1e-4m) = .0001m | 1m = 1000mm => .0001m*1000 = .1mm | [deleted] | Retric wrote: | Ops, 100 ( 1 millionths of a meter) is a much more | reasonable tolerance than 1 / 100 millionths of a meter. | | I am to used to people saying 100 millionth of a meter to | mean 10 nm. | dekhn wrote: | millionths of a meter are known as micron so most people | would call this '100 micron' (or '100 micrometers') which | is indeed close to 4 thou, as you calculated, and is the | level of accuracy of my ~$500 3d printer. | | 1 thou was achievable in routine shops in the 1940s and a | tenth of a thou (2.54 micron) is a common accuracy to | target these days. Obviously it depends on the context | and the size of the object, at some point you move away | from cutting to using grinding and lapping to achieve | your results, which is ultra-timeconsuming. | StackOverlord wrote: | > Dr. Ning Li of Huntsville, AL passed peacefully away on | July 27, 2021. She was 79 years old. One of the world's | leading scientists in super-conductivity anti-gravity. Dr. | Li had constructed first 12" HTSD of the world in late 90s. | | https://www.berryhillfh.com/obituary/ning- | li?lud=4CF765EE88E... | themagician wrote: | I find the geometry of things like this fascinating. We | typically think in such simple shapes. I feel like my brain can | do triangle, rectangle and maybe hexagons and that's about it. | I remember when I finally understood radians enough to really | understand circles and waveforms--I felt so enlightened. Like I | actually remember the moment when it clicked. For years I was | just "doing the work" without actually understanding what I was | doing, but once I was able to understand it... it's like | something changed in my brain. | | I want to be able to think in mobius, but my brain is currently | like, "No thanks." | sdwr wrote: | I'll argue that "thinking in mobius" is simpler than thinking | in circles, and more true to life than thinking in basic | shapes. | | The core concepts in mobius-land are local curvature and | global cumulative field. | stjohnswarts wrote: | Sorry those just aren't the way the average joe on the | street thinks about things. | KyleBerezin wrote: | Yea they are kinda confusing, especially when you get into | the 3D ones like klien bottles and roman surfaces. I also | recently learned that if you make a mobius shaped | transmission line (like a ladder line) and you send a pulse | down it, that pulse will continue looping until it dissipates | (or forever if it is a superconductor). | | https://www.microwavejournal.com/articles/21001-printed- | reso... | | I have no idea if there are any advantages over a simple | planar circular loop though. | colordrops wrote: | Are real life superconductors ideal, i.e. they truly would | store a charge forever (at least until the material | disintegrated)? Or is there some sort of loss, albeit much | less than typical resistance? | dekhn wrote: | I can't really think in (visualize) 3d shapes, so I depend a | lot on 3D geometry programs when I design things like for my | microscope. A fair number of people I've talked to can | visualize complex shapes in their head, rotate them around, | do interference checking, etc. | willis936 wrote: | They're actually quite simple geometries in the right | (unintuitive and warped) coordinate system. | eternityforest wrote: | Doing CAD design is really interesting. A lot of stuff is | just 2.5D, extrusions of 2D sketches sitting on other 2D | sketches. | | Then you accidentally make something truly 3D by intersecting | things and realize you have no idea what you're looking at, | couldn't imagine it if you closed your eyes, couldn't | replicate it if you had a picture of the result and didn't | know the 2D inputs that made it... and then you realize there | are probably people out there who can see that entire design | in their head. | | To me it's like unicycling on a tightrope or skateboarding or | realistic oil painting or playing piano well. I have no real | concept or reference point for what that experience must be | like. | p1mrx wrote: | Just drawing a 3D slanted plane to match the front of my | printer made my head hurt: | https://www.printables.com/model/526981-ender-3-s1-quad-z- | br... | waldothedog wrote: | Interesting. With a very strong reference for the | experience of skateboarding, reading your sentence made me | think about how hard it is to explain! I suppose when it's | going well, it feels like body/mind flow, when it's going | poorly it feels like physics :) ___________________________________________________________________ (page generated 2023-08-11 23:00 UTC)