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Comment by tomas789 | Hacker News Reader

I was recently listening to a researcher talking about ITER. He claimed that there is currently no technology to shape high temperature superconductors into usable coils. Reason was their mechanical properties, namely fragility. He also claimed that all commercial fusion reactors are either using those or He3 which would need to be mined from the moon.

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The claim about the second is correct, the first not quite since there are a few mid temperature superconductors that do work in liquid nitrogen, and REBCOs are mechanically good enough. Their problem is all the rare earths - and to make a magnetic containment fusion reactor you need truly massive coils. So you face a problem in price and availability of the materials...

> Their problem is all the rare earths

The fraction of mass in a HTS magnet that is rare earth is surprisingly small. Most of the mass is mechanical support, or substrate on which the thin HTS film is deposited. The entire ARC reactor might contain 10 kilograms of REBCO (2015 paper), out of a reactor mass of over 7 gigagrams.

https://arxiv.org/pdf/1409.3540

Helion would make their own 3He, by DD fusion. No lunar mining needed.

Yeah and where are those over unity results of their test reactor?

The other thing is that we do not care as much about the fuel, but the sheer masses of liquid helium as coolant. That reactor is not designed to capture the helium made for this purpose while staying energy efficient.

Helion has not yet built a reactor that would achieve the conditions needed for net energy generation. I hope the person he was talking to was talking about prospective reactors, not currently existing ones, as the latter is the null set.

Helion's design doesn't use superconducting magnets of any kind.

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