Do I understand correctly that they haven't actually fused anything yet, just verified that the stellarator can power up without immediately exploding?
What's special about the Wendelstein 7-X? I know stellarators as a concept aren't new. Is this a significant result, or is it just a handy opportunity for a media event?
Cliffnote version is: stellarators are hard/expensive to build. The test run shows this one seems to be built correctly.
Simplifying a ton one could compare the two competing designs as follows:
stellerator: harder to build, easier to run (and more efficient)
tokamak: easier to build, harder to run (and less efficient)
Due to the first property, there are more tokamaks around and showing basic functionality for any stellerator is a good/important step.
Edit (relevant quote from the article):
"""Although there are about a dozen stellarator experiments around the world, including in the U.S., Japan, Australia and Europe, scientists say the Greifswald device is the first to match the performance of tokamaks."""
The number of functional stellarators is rather limited, so getting it built is a success in itself. W7-X will be the largest of the bunch and is supposed to sustain plasma for up to 30min (for comparison, the record for tokamaks is 6.5min, and ITER will only add a minute or two to that).
I don't think they generated any fusion reactions, I believe they used just natural Hydrogen rather than Deuterium and Tritium (which would normally be used for fusion fuel). Also, magnetic confinement fusion reactors don't explode, they are like pencils balanced on their points, when something goes wrong or they "lose containment" the pencil falls over, the fusion conditions dissipate and reactions stop. This test was just one step along the way of verifying the plasma dynamics and heating capabilities of the system, it'll be a while before they do fusion reactions, and it will never produce energy from fusion. But be aware that making fusion reactions happen is easy, it's the matter of creating a self-sustaining fusion reaction that's hard.
In magnetic confinement fusion there is a big problem of confinement stability. You are trying to confine a plasma, which is electrically charged and thus an electrical conductor. Electric current generates a magnetic field. This is actually made use of in tokamak designs, which are the most straightforward magnetic confinement systems. However, tokamaks suffer from a fundamental flaw, that plasma current produces a feedback instability loop making it very challenging to attain plasma confinement longer than a few seconds or minutes. That's problematic because the shorter lived the fusion plasma is the more the initial (externally produced) heat as a proportion of the total cumulative heat of the plasma over its lifetime adds up. Short lived plasmas don't spend very long producing fusion heat to "pay back" the energy used to heat up the plasma to fusion conditions to start with.
A stellarator is basically a way to twist the magnetic fields around the fusion plasma tube in such a way so that the trajectories of ions in the plasma will stay inside the confinement volume, without requiring any current in the plasma. This makes the system potentially much more stable but at the cost of a very much more complex arrangement of magnets. The longer the plasma can be confined the longer fusion reactions can be sustained, making it easier to generate more power than was put in to raise the plasma to fusion suitable conditions (high density, high temperature).
> This is actually made use of in tokamak designs, which are the most straightforward magnetic confinement systems.
Wrong! The most straightforward magnetic confinement systems are :
- Simple toroid design -> Have some flaws that make useless and Stellerator is a evolution of the idea, fixing it with twisted magnetic fields.
- Magnetic mirrors -> Two simple coils separated, so the combination of the shape and the more dense magnetic field on the center of the coils, works like a mirror for charged particles.
Also, at nearly the same time (around 1955) that the Russinas was begin to experiment with the Tokamak design, the British was experimenting wit the "ZETA", where the contaiment magnetic field comes ONLY from a current on the plasma.
Huh, that last part sounds kinda interesting. Pardon my scientific ignorance, but is that 'self-containing plasma' phenomena the reason why our Sun hasn't exploded yet?
It's a few grams of plasma, and it's inside of a huge metal contraption. If you "lose containment" the plasma just expands, contacts the walls of the reactor, and cools off. It's kinda bad for the reactor because high temperature plasmas tend to chew through materials, but fusion reactions stop, it's a non-event outside the reactor. In fact, losing containment is typical, modern fusion reactors can't contain plasmas very long, only a few seconds. The normal operation of a reactor is magnetic containment for a few seconds, then loss of containment, followed by later "shots" of fusion plasma being contained and heated for another few seconds, and so on.
> What's special about the Wendelstein 7-X? I know stellarators as a concept aren't new. Is this a significant result, or is it just a handy opportunity for a media event?
The concept is not new, they're just hideously complicated to build. It's a relatively new development that it's possible to model the shape of the magnetic fields and magnets required to keep the plasma. So it's a significant achievement to build one and prove that you can run it while containing the plasma. Yesterdays event is one step on that path.
W7X is special as it is more performant than previous stellarators. For fusion devices, you hope to produce more energy than the energy you have to inject to heat the plasma for fusion to happen.
Yesterday's event was not much about science, but rather about engineering. Building that machine was a gigantic work.
> For fusion devices, you hope to produce more energy than the energy you have to inject to heat the plasma for fusion to happen.
Which Wendelstein can't do – for that, you'll need much more radioactive reactions (involving tritium), and Wendelstein isn't (and can't be) sufficiently shielded for those.
Wendelstein is a research reactor: It's covered in sensors in and out, and it can be easily disassembled or opened up for repairs and modifications, which you generally don't want to do if everything's covered in radiation activated materials.
If Wendelstein holds up to its plans, derivative designs can be used to build net-positive reactors involving tritium (and lots of shielding).
> Yesterday's event was not much about science, but rather about engineering. Building that machine was a gigantic work.
Indeed. Most of its design was finalized in the 80s and the project took 25 years to just get the funding, build the (first of a kind) components and build a working reactor out of them.
In programmer speak, you're essentially asking for how long will it take to implement some new feature (let's say collaborative text editor) in language unknown to you :P
This humorous answer for fusion is 50 years. Always another 50 years.
Realistically, there has been much more progress recently including several SV style startups with massive funding trying to get things to work. It probably is within 50 years this time with the amount of real money and research going into it.
The article says that the 7X won't ever produce energy. Over the course of the following years they will try to leave it on for longer and longer period of time.
SO yes, they kept it on for less then a second, nothing exploded and future looks quite brigth i would say
Don't let movie physics fool you. Fusion reactors don't have a tendency to explode. (Well, at least not any more than any other industrial device connected to megawatts of power...)
The problem with fusion is that they are notoriously hard to achieve, so basically they are always in the brink of fizzling out.
They've been doing test fires with helium to clean the inside of the stellarator for the past few months. This news is because yesterday, with hydrogen, they ran a plasma at 80million degrees for 0.25 seconds. Still a few years away from the goal of 100 million degrees for 30 minutes, but it's a huge achievement. When that's working they'll start putting deuterium in and the fusion fun will begin, but not at a level that actually has a net energy output. That will only happen with tritium, but that won't ever be done in this particular stellerator (at least there aren't any plans to do it).
What's special about the Wendelstein 7-X? I know stellarators as a concept aren't new. Is this a significant result, or is it just a handy opportunity for a media event?