10 ms·
Tests show high-temperature superconducting magnets are ready for fusion
- gpm 3y agoIs there a good reason we aren't seeing REBCO magnets in all new MRI machines? Seems like not needing liquid helium would be a pretty big win for hospitals?
- fabian2k 3y agoThey probably still can't carry the necessary current without helium cooling. There are some NMR spectrometers (which work essentially by the same principles as MRI machines) with high-temperature superconductors, but those are still cooled by helium. The lower the temperature is the more current you can pack into those. Could also be that it doesn't make economic sense yet, they're still pretty new compared to classical superconductors.
- refulgentis 3y agoYes: Commonwealth Fusion essentially is buying the world's supply of it. MRIs are a more mature market, i.e. > 1 units, and need to justify component switches not just for feasibility, but for profitability. Swapping out a known-good for something in such short supply isn't feasible, it's more expensive than liquid helium. Source: https://spectrum.ieee.org/fusion-2662267312 https://spectrum.ieee.org/fusion-2662267312 "Over two years, the team managed to buy up most of the world’s supply of 4-millimeter-wide HTS tape"
- actionfromafar 3y agoCommonwealth Fusion is such a Fallout name
- deprecative 3y agoTodd is in shambles that he can't use the name.
- fragmede 3y ago[flagged]
- cyberax 3y ago> Is there a good reason we aren't seeing REBCO magnets in all new MRI machines? REBCO tapes are still very brittle, and MRI machines are notorious for the amount of banging they produce when active.
- andbberger 3y ago??? the gradient coils make the noise, and due to field homogeneity requirements, it is safe to assume the superconducting coil is not moved by the gradient coils
- alacritas0 3y agohomogeneity is only optimized for a small volume within the bore. Regardless, the superconducting coils will still experience a change in Lorentz forces as sequences are run, and noise from other components will still be "heard" by the main magnet
- cyberax 3y agoIt's still very much affected by the vibrations, and the electromagnetic forces from the gradient coils.
- caymanjim 3y agoMRIs don't consume much helium. Keeping them topped off is a trivial expense compared to the rest of the costs of the machine and operation. If there were a new design that didn't require helium, it would also have to cost less than current machines to make sense.
- 7speter 3y agoWait, isn't the byproduct of fusion helium anyway?
- willis936 3y agoYeah but you'd power a city for a year for 100 kg of helium.
- ta988 3y agoA single MRI needs around 1000 liters, 1L is roughly 130g. For those who wonder prices vary between $15-35 per liter. Recent MRIs have recycling systems that reduce refill needs by 90% when they work properly.
- willis936 3y agoSo about $15k for 100 kg?
- Tuna-Fish 3y agoFusion produces much, much less helium than that. D-T fusion that produces 100kg of He-4 would produce something like 25PJ of net primary energy. If you managed to turn 20% of that into electricity, you'd have 5PJ. This is within an order of magnitude of the yearly electricity consumption of the entire world.
- willis936 3y agoI do actually have receipts. For example numbers I picked Washington DC, which has 700k people that each use an average of 600 kWh per month. That's 5 TWh / year, which I rounded up to 10 TWh. This yields 475 m^3 of helium, which is 85 kg. I rounded up to 100. DC is a modest city and all of humanity uses 15000 TWh / year (of heat). This "100 kg / city / year" estimate is even on the lower end since I started with electric consumption and never put in the factor of 3 to convert to thermal. Your mass-energy conversion number is within error of mine, but your estimate of how much power we use is much lower. https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817.59+MeV%29+%2F+%28avogadro%27s+number+1%2Fmol%29+*+%284.002602+g%2Fmol%29+%2F+%280.1786+g+%2F+liter%29 https://www.wolframalpha.com/input?i=%2810+TWh%29+%2F+%2817....
- ororroro 3y agoThere are already non-venting systems that use a reasonable amount of helium (7L) to manufacture and don't require refilling. It just was not a design consideration previously. https://www.philips.com.au/healthcare/resources/landing/the-next-mr-wave/sealed-mr-technology https://www.philips.com.au/healthcare/resources/landing/the-...
- pfdietz 3y agoI would say it's because the technology has not been matured enough. I would also say the reason CFS has been getting funding is not because of fusion (although, hey, why not take that longshot bet), but because of the value of being able to make these magnets for non-fusion applications.
- CrzyLngPwd 3y ago...in thirty years.
- deleted 3y ago[deleted]
- refulgentis 3y agoPeople have been saying this for 5 years on every Commonwealth Fusion article as they hit every milestone exactly on time. It's happening this time, people rushing to make fusion jokes are getting downvoted because it's apparent you're just keyword-matching fusion then snarking.
- pfdietz 3y agoThe problem I have can be see by going back to the original ARC paper. That reactor was much smaller than ITER, and had 10x power density, but was still the mass of several WW2 destroyers (for net 190 MW(e)). Its volumetric power density is still 40x worse than an existing commercial PWR.
- dotnet00 3y agoI think they're getting downvoted because the joke is getting really worn out and endlessly dismissive cynicism is just annoying.
- deleted 3y ago[deleted]
- gerdesj 3y agoI went to Abingdon School, which is quite close to Culham labs (JET) in Oxfordshire, in the mid 1980s. One of my A levels was Physics. We had some boffins from JET pop on over and do a presentation to us about what they were up to. I was one of the thickies. Some of my (then) compatriots are now dons and even proper scientists! I only managed a random walk into IT. I dimly recall a graph showing progress on how they were able to fire up the thing and the energy out compared to energy in. That graph had quite a decay on it initially but a really long tail. That long tail is where the always 25 years off meme comes from. Nuclear fusion as an energy source is a massively complicated beast. You might like to note, say, that building for Hinkley Point C (a fission plant, Somerset, UK - just up the road from here) was started late 2018 and was due to be commissioned in 2023 and now is due in 2030. You might also note that aircraft and the like tend to take 20+ years to go from concept to service. A nuclear fusion plant will take quite a while to commission once a concept has been thrashed out. Perhaps CF have got it sorted but there is a damn good reason for the always 25 years off "joke" - I was told it over 30 years ago by physicists working and already long time served at the coal face.
- catchnear4321 3y ago> only needs hydrogen atoms for fuel rather than rare and dangerous elements like uranium and plutonium hydrogen isn’t exactly the safest element. not that any element is truly safe if used in the wrong way.
- porkbeer 3y agoHow is it unsafe? I just electroplated on my desk and hydrogen was formed (right next to pure o2) with zero danger. Sure, an accumulated mix near stoich might be an issue, but that is easy to avoid.
- catchnear4321 3y agoand you can split water and make neat bubbles of two elements. more likely to shock yourself than make a boom. most elements are safe if you handle them properly. that assumes nothing outside of your control. and no one.
- maximus-decimus 3y agohttps://www.youtube.com/watch?v=fURATK5Yt30&t=173s https://www.youtube.com/watch?v=fURATK5Yt30&t=173s
- u320 3y agoSo he's pushing an energy solution that requires Tritium. One of the rarest elements of earth. And then has the nerve to accuse fission of relying on rare elements.
- refulgentis 3y agoWho is he? Where did he push tritium? Is the word tritium in the article? (Chrome can't find it.) Is hydrogen more common than uranium? Is hydrogen more common than plutonium? What quote demonstrates "accuse", as in, "they had the nerve to accuse"? These are honest questions, I hope you don't take offense. Full disclosure: I live in Cambridge, MA, where MIT is located.
- dang 3y agoUrl changed from https://futurism.com/the-byte/mit-magnets-ready-fusion https://futurism.com/the-byte/mit-magnets-ready-fusion, which points to this. (Normally we prefer the best third-party article to a corporate press release but the balance of information here points the other way.) Edit: I should say that if there's a more informative third-party article, we can switch to that.
- bananapub 3y agoI really wish people involved in fusion research, and their university/corporate PR colleagues, had not spent the last forty years poisoning the fucking well. fusion power is still so far away that it can't even figure in to our plans for reducing emissions to zero, and yet people still publish articles like this to muddy the waters and make it sound like it matters in the short term at all.
- cubefox 3y agoThe real question is whether it can ever compete against fission in terms of cost. Currently it looks like fusion power plants will be substantially more expensive than fission power plants.
- Certhas 3y ago... which is considerably more expensive than solar + hydrogen.
- cubefox 3y agoHydrogen for power storage is hardly used in practice, so it is probably quite expensive. Overall, solar energy seems very expensive when you factor in storage cost. Germany has very high energy prices, likely related to switching off fission power plants and heavily investing in intermittent energy sources like wind and solar.
- Certhas 3y agoLikely related to? As in you pulled this idea from thin air and pop science reading? Electricity prices are mostly political. Fossil has been heavily subsidised throughout its lifetime, as has nuclear. French prices are lower because their energy producer has 70 billion in debts, backed by the French state, in order not to pass the true price of nuclear on to consumers. Hydrogen is not used yet, because we don't have enough renewables to have significant overproduction. For now storage is not needed. Truly this is a topic where everyone feels comfortable to throw in strong opinions without having even the slightest idea of how any of it works.
- u320 3y ago> "Overnight, it basically changed the cost per watt of a fusion reactor by a factor of almost 40 in one day," So there is this myth that fusion enables unlimited cheap energy. This is 100% false. It's not unlimited at all. Most concepts relies on using lithium-6. That's not a super common element. But more importantly, it's not cheap. That should be obvious, if you could reduce the cost per watt 40x and still not be competitive.
- ianburrell 3y agoLithium is a super common element. They are mining tens of thousands of tons per year increasing rapidly as make electric car batteries. Lithium-6 is 5% of lithium. Fusion reactors only need tons for breeding blanket.
- pfdietz 3y agoThe original ARC design had 950 tonnes of FLiBe, which contains 115 tonnes of Li-6. This is a substantial fraction of the Li-6 produced for the entire US hydrogen bomb program, all for a single 190 MW(e) (net) reactor.
- Tade0 3y ago115 tonnes of Li-6 is what you get by sifting through the lithium required for ~200k electric cars. Tesla alone could provide material for nine such reactors annually.
- pfdietz 3y agoSure, the input feed is not the problem. The problem is actually separating it. The technology used for the H-bombs is no longer acceptable due to mercury pollution. World Li isotope separation capacity currently is in kilograms per year (to produce pure Li-7 for pH control in fission reactors.) And then there's the beryllium. A single one of those ARC reactors would use something like 40% of the current world annual beryllium production.
- pinewurst 3y agoIt’s interesting that it took 3 years from the physical test until paper publication.
- deleted 3y ago[deleted]
- probablypower 3y agoPublications often take a long time. Particularly novel topics that are difficult to review due to a lack of comparative material or willing expertise. The fact that it took 3 years is a positive, as it means multiple parties rigorously reviewed and approved the material.
- saagarjha 3y ago[flagged]
- Certhas 3y agoIf someone is knowledgable on this: What does this mean for ITER? Any chance to retrofit new magnetic technology into ITERs design?
- johnbcoughlin 3y agoIt means nothing for ITER unfortunately. Changing the toroidal field strength implies a totally different plasma size, density, temperature, everything. ITER isn't designed for this strong of fields and the plasma they would confine.
- elihu 3y agoI'm not super knowledgeable, but my understanding is that ITER was designed around the best superconductors known at the time, which meant making the whole thing really big. A benefit of stronger magnets is that you can make it a lot smaller, and presumably cheaper -- which is what MIT has been working on with SPARC. I don't know if it's practical to upgrade the magnets on ITER, but I'd expect it to be really expensive -- especially if they've already manufactured/installed the old magnets.
- pfdietz 3y agoIt would be completely impractical, since ITER is not designed to withstand the much larger JxB forces (which scale as B^2). In the high Tc high field designs, the mass of the metal supports for the magnets dominates the reactor mass.
- Certhas 3y agoThank you, that's the kind of point I was looking for. Why does JxB scale quadratically? Because a stronger field can contain (linearly) more current?
- pfdietz 3y agoIf you double the current J, you double the magnetic field B. But the JxB force is now quadrupled, because you doubled both J and B.
- p1mrx 3y ago> Like virtually all electrical wires, conventional superconducting magnets are fully protected by insulating material to prevent short-circuits between the wires. But in the new magnet, the tape was left completely bare; the engineers relied on REBCO’s much greater conductivity to keep the current flowing through the material. Much greater conductivity than what? I assume there are other non-REBCO layers in the tape, but the article neglects to mention them.
- deleted 3y ago[deleted]
- glatisaint 3y agoMuch greater than previous superconductors I would assume.
- Tuna-Fish 3y agoStainless steel. Which is a perfectly good insulator when the alternative is REBCO.
- willis936 3y agoPresumably the hastelloy substrate. https://www.nature.com/articles/s41598-021-81559-z/figures/6 https://www.nature.com/articles/s41598-021-81559-z/figures/6
- baking 3y agoDuring a quench, almost all of the current is carried by the copper cap. https://ieeexplore.ieee.org/document/10316632 https://ieeexplore.ieee.org/document/10316632
- Animats 3y agoThan stainless steel! If you have two resistors in parallel, the current in each is proportional to the ratio of the resistances. But what if one of the resistances is zero? Then all the current goes through that resistor. So if you have a superconductor in parallel with another resistor, all the current goes through the superconductor! Doesn't matter if the other resistance is very, very low, but still nonzero. Reportedly some undergrad thought of this. So the superconducting layer is bonded to stainless steel tape, which is strong, not brittle, and will go down to cyrogenic temperatures without problems. Most previous superconducting "wires" had brittle ceramic insulation, which was hard to wind into magnets. This is really clever.
- elihu 3y agoIt's kind of funny that that image looks an awful lot like the housing of a Mazda rotary engine. I'd be curious if MIT / Commenwealth Fusion have made any progress on their "remountable magnets" approach. The problem is that if you have to replace parts of the reactor, the magnets get in the way. I think they found that you could just solder the ends of REBCO film to each other and even though the solder isn't superconducting, the layer can be thin enough that it doesn't matter. So, they were looking at technology to take a tokomak apart by desoldering the REBCO, then they can replace whatever parts are inside, then solder it back together when they're done. That seemed like a pretty hard problem, and not one they're trying to solve with SPARC (which is only meant to be a cheap prototype reactor, not something designed for a long service lifetime).
- tw04 3y ago> It's kind of funny that that image looks an awful lot like the housing of a Mazda rotary engine. You at least have to give the poor guy credit :). Wankel engines can be found all sorts of places including planes! https://en.m.wikipedia.org/wiki/Wankel_engine https://en.m.wikipedia.org/wiki/Wankel_engine
- elihu 3y agoSure, but I've only seen variations of the Mazda 13B disassembled up close. I don't know if other Wankel engine housings look quite the same.
- moab9 3y ago[flagged]
- mcnamaratw 3y agoWhy? MIT could just rein these people in, and the reputational damage would stop right away.
- fallingfrog 3y agoBSSCO is superconducting at much higher temperatures. Why are they not using that?
- GlibMonkeyDeath 3y ago"In practice, HTS are limited by the irreversibility field H, above which magnetic vortices melt or decouple. Even though BSCCO has a higher upper critical field than YBCO it has a much lower H (typically smaller by a factor of 100)[11] thus limiting its use for making high-field magnets." https://en.wikipedia.org/wiki/Bismuth_strontium_calcium_copper_oxide https://en.wikipedia.org/wiki/Bismuth_strontium_calcium_copp...
- nielsbot 3y agoI saw this presentation by Dennis Whyte years ago and it left me really optimistic about Sparc/Arc's chances... He goes through a lot of the interesting design details, including why REBCO is such a huge difference and will make their commercial reactor design possible: https://www.youtube.com/watch?v=KkpqA8yG9T4 https://www.youtube.com/watch?v=KkpqA8yG9T4
- bmitc 3y agoThe only thing is that there are tons of problems beyond just having strong magnets. Using REBCO tape for the magnets indeed solves the problems of reactor size by letting the reactor be much, much smaller than say ITER. But it does not solve the other problems of reactor design and operation.
- nielsbot 3y agoI'm sure that's true.. but at least in this presentation they seem to have thought through most of them? I want to believe :)
- bmitc 3y agoThere are huge hurdles in maintaining reactors, even once you get them going in the first place. The fusion reaction causes many components of the reactor to decay and lose performance or fail.
- pfdietz 3y agoAnd makes the reactor so radioactive no one can get in to repair anything that breaks.
- pauljurczak 3y ago20 K is high temperature? Well, I better take my mittens and ushanka off. I thought 77 K was the official threshold: https://en.wikipedia.org/wiki/High-temperature_superconductivity https://en.wikipedia.org/wiki/High-temperature_superconducti....
- willis936 3y agoYou'd never operate a superconducting magnet at its crtical temperature. Check out figure 5 here. The relevant bit is the vertical slice along the left edge. Crtical current density and internal magnetic field both go way up when you go below LN2 temps. You could make an LN2 HTS magnet, it just wouldn't be in the 1T+ class. https://cds.cern.ch/record/2277484/files/Bruker%20HTS%20Fit.pdf https://cds.cern.ch/record/2277484/files/Bruker%20HTS%20Fit....