Major nuclear fusion milestone reached as ‘ignition’ triggered in a lab

Re:Major nuclear fusion milestone reached as ‘ignition’ trig... by ckuehne on Tuesday October 12, 2021 @12:16PM (#28841521)

I think your statement "Once you have plasma breakeven you have a self-sustaining heater basically" is false. According to Wikipedia [1] - if I interpret it correctly - the fusion energy gain factor from plasma must be 5 (!) to have a self-sustaining heater:

"Most fusion reactions release at least some of their energy in a form that cannot be captured within the plasma, so a system at Q = 1 will cool without external heating. With typical fuels, self-heating in fusion reactors is not expected to match the external sources until at least Q = 5"

[1] https://en.wikipedia.org/wiki/Fusion_energy_gain_factor

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Re:Major nuclear fusion milestone reached as ‘ignition’ trig... by mlindner on Tuesday October 12, 2021 @02:02PM (#28842941)

I oversimplified in that statement, you need more than a factor of 1 because of heat losses to the environment yes. However 5 is not much different than 1. We've gone from 0.0001 only a few years ago to close to 1 now.

And btw, you really want more than 5, 10 or 20 ideally, but again, that's not too hard as compared to how far we've come and new reactors will be beyond that soon.

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Re:Major nuclear fusion milestone reached as ‘ignition’ trig... by willis936 on Tuesday October 12, 2021 @01:38PM (#28842591)

Fusion begets fusion. ITER plans to have high-intensity, relatively short Q=10 shots. If the plasma heats itself then it doesn't need much heating. This sudden focus on Q is clearly the result of one vocal non-expert not understanding the field and everyone listening to them like they have something valuable to teach.

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