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Comment by yaniqt | Hacker News Reader

Is it possible they subtracted the energy required to facilitate the reaction in the first place? So net energy was enough to boil 60 kettles worth of water?

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"At Jet, two 500 megawatt flywheels are used to run the experiments."

So net power is -989MW, assuming both flywheels are at full pelt the whole time and no power is required before fusion is acheived.

Those are used for the confinement coils. Incredibly, JET uses copper coils. You can't run those all day, so the flywheels are used. The last machine I worked at worked the same way. 16 train motors with 1 ton flywheels spinning at 1600 RPM to be an 11 MW power supply for 1 second every few minutes.

Plasma heating in JET is done via NBI+ICRH and is about 59 MW.

I've seen those copper busbars -- they drill holes for water throughout them. The whole design of high-B field environments is fascinating; you end up with things like Bitte designs with split rings and a whole lot of engineering to stop the copper vapourising. Highly recommended if you're ever in the area – they do two sorts of tours (or did, prior to covid), the "general public" tour and the "scientist" tour. I went on the latter. The sight of two giant robotic arms playing Jenga to train their operators is not one to forget.

I should visit JET sometime. Of all the systems on the machine I worked on (https://hsx.wisc.edu/), the coil current feeds were the most difficult. Trying to cram that much current through a small piece of copper with a discontinuity takes years of effort.

That would be a fusion breakthrough worth mentioning on its own.

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