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Comment by NextHendrix | Hacker News Reader

"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.

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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.

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