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.
'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.
The first Alternativlos Podcast of two conducted with the leader of the Wendelstein X project relates how certain magnetic coils were purpose made by a kind of emeritus engineer in Swiss. Which seems corollary to the common wisdom about EMI, it's magic, so the manufacturer must be a wizard.
On the other hand it is reminiscent of a Georgian I met who used to be occupied with winding regular tire sized coils by hand, for over land transmission lines. This is chirurgical precision, literally hand-craft.
We do a lot of thinking with our hands. It stands to reason, metaphorically speaking, that Wendelstein is an experiment to gain hands on experience. Therein lies the difference to megalomanic projects that exceed initial estimates, eg. BER airport, which are a running gag by now.
Insolvency means the investment returned no profits so investors on those projects stopped paying. It likely doesn't mean that the cheques bounced on liabilities. And it obviously doesn't mean that investment in this space had to stop.
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.
They could go longer. 7-8 mins is an arbitrary cut off out of fear that something might break (quench), knowing that enough data has been gathered for the time being.
W7-X is a new stellarator design. It’s magnet arrangement was optimized using a lot of compute time and is designed to overcome the faults of previous more naive designs.
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.
The main problem with stellerators is their murderous complexity. You need to manufacture several thousand different parts with complicated 3D geometry, micron-level precision, and from unobtanium-class materials.
All while not being able to properly simulate the outcome on a computer.
Stellarators are superior to tokamaks, so an energy-positive stellerator will be about 2 times smaller than a tokamak. But we're still talking about a building-sized vacuum chamber.
That's why for ITER it makes sense to go with a simpler design to de-risk the main objective: building a burning plasma laboratory.
Doesn't really track. Stellarators can operate above the Greenwald density limit. They just have shorter confinement times for a given field strength and major radius.
