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Phage0070 t1_iy932ft wrote

Cooling magnets is important when those magnets are superconducting electromagnets. An electromagnet produces a magnetic field by passing electricity through coils of wire. If you want a powerful field you need a lot of electricity, and to do this efficiently you want the coils of wire to have low electrical resistance.

The magnets on the ITER use huge amounts of electricity, enough to just melt normal wires into a puddle. Instead they are made out of superconducting materials which have basically zero electric resistance. They need this in order to work, but the only materials we know of that can be superconducting are only that way when very cold. Keeping the magnets cold then is crucial to them working at all.

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mmmmmmBacon12345 t1_iy9qvam wrote

>Instead they are made out of superconducting materials which have basically zero electric resistance.

There's a pedantic but critically important bit here that super conductors have actually zero resistance as long as they're below their critical temperature which means they don't dissipate any heat which is what lets them carry the crazy currents needed for the strong magnets

As soon as any part passes the critical temperature its resistance becomes not zero, it starts dissipating a ton of power, the helium nearby flash boils, more of the magnet heats up, and everything comes crashing down in a sad magnetic quench that tends to damage everything

So the magnets are cold because if they're not super cold then they're resistors not magnets and they instead get super hot

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druppolo t1_iya0s5d wrote

Like throwing a cigarette into kerosene, one degree less and it’s all fine and one degree more goodbye room.

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