I have been reading articles describing the progress made towards fusion energy and got intrigued by how they do it.
https://www.msn.com/en-us/money/other/nuclear-fusion-reactor-sustains-plasma-at-100-million-c-for-30-seconds/ar-AA11BpC8
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The plasma created by the fusion is magneticslly charged and can be contained and routed via superconducting magnets in a device called a tokamak. That contains much of the energy. Additionally the internals are reinforced steels designed to take reduced damage from fusion heat and neutron bombardment.
I do not know how long one could continuously. I think the longest contained fusion reaction was under 15 minutes so far.
It is levitated with magnets in a vacuum chamber with essentially no air and thick shielding around it with a lot of cooling loops.
You can measure the temperature by the radiation it emits. Kinda like how a blue flame is hotter than an orange one.
I used to study this at uni (nuclear engineer here) but i’m a bit rusty.
Consider that talking about temperature in plasma is a bit more nuanced than “normal” day-to-day temperature.
Hot means: it makes my atoms vibrate faster.
What happens if my atoms vibrate so fast that they get flung into space? Is it still hot or something different?
In general, temperature is linked to kinetic energy of the particles by a linear relation (temperature = energy * adjustment variable). But in gas, liquid and solid, you have fairly big (atoms, molecules) particles moving at a slow pace compared to their size.
So if you touch it, you interact basically by conduction, and feel the heat, thus a concept of temperature.
On a plasma for nuclear fusion, you have free electrons and protons (many time smaller than atoms) zooming by, close to the speed of light.
Getting close by, you will never get to “touch” them, they emit very high intensity beams of light that are strong enough to damage materials but so “tiny” that your temperature sensor (e.g. the nerves) might not be able to perceive it.
If you try and “touch” the plasma (don’t do it, it is very unhealthy to do so) it would move so fast and be so tiny that most of it would pass through you as if you were not there.
So the temperature you read is more a description of the speed of the electrons and protons running in circle at crazy speed, than a sensorial experience.
Infact scientists don’t measure it in celsius or kelvin, but in eV (electron volts) that is a measure of energy.
1eV = 10’000 C more or less.
Of course this mad running releases energy in form of invisible (x-rays gamma-rays) light that hit the metal casing and cooling fluid, heating them up.
I suggest that you should cosider the plasma “fast” rather than “hot”.
Fusion will be like a jet engine. Jet engines take power from the fire and use most of it to keep the engine going. Then the left over power pushes the airplane. The fire and hot gases would melt the engine if they touched the little spinning wings inside. careful design and engine power keeps the engine from getting too hot.
Fusion generators will use most of the electricity they make to keep the fusion engine safe. Strong magnets will keep the tiny little ribbon of heat in the middle of a box while other machines take the heat away to make electricity. I wonder if they might even spin like a jet engine.
It’s an excellent question. Fusion plasma is basically the Universal Solvent, able to dissolve any known material due to the insane temps and pressures… and this includes its container.
There’s a couple strategies. The first is magnetic confinement. Basically it’s held in place by a magnetic field, so the plasma never actually touches anything physical. This comes with its own set of problems. First, there’s a tremendous number of neutrons that are still flying off and crashing into the walls which still degrades them. Next, shape of the magnetic field is very important. That’s why some varieties are really strange looking. Finally, you need really strong magnetic fields and the way to make the strongest magnet fields is to cool down the magnetic materials to near absolutely zero. But think about that… now you have to maintain the temps and pressures of a star mear centimeters from materials at near absolutely zero. And people wonder why fusion is perpetually 20 years away.
There are other strategies to contain the plasma though, that approach it in different ways. General Fusion has revived an old idea. Basically they surround a sphere with really strong pistons and all those Pistons are coordinated to slam into a liquid metal medium (I think they’re using lithium) which concentrates and focuses the shockwave onto a tiny bit of material at the very center. Each time there is a pulse the material undergoes a burst of fusion. The liquid metal then absorbs the bursts of heat and can be circulated to extract the heat from the pulsing bursts of fusion. This way your container walls never go bad because you can continually flow more liquid metal in as needed.
I’m sure there’s other strategies, but these are the two I’m most familiar with.
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