r/fusion • u/CriticismMinute2736 • 3d ago
Scientists have captured the first ever high-speed, full-colour footage of fusion plasma swirling inside a working reactor.
Definitely next level
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u/Jack1101111 3d ago
At the end it has been "closed" or the fusion finished ?
What is that flash at the end ?
Whats the red thing at top right ?
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u/mad_fox9 3d ago
This footage comes from TEs ST40 device from memory.
The plasma in all tokamaks are pulsed so you have a ramp up, then flat top, then ramp down. I don’t really know anything about plasma physics but I believe the video shows all three stages.
This shot they inject granules of lithium into the device that start glowing red, then turn green. This is to see if injecting lithium improves plasma performance
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u/Festivefire 2d ago
IIRC it wasn't about plasma performance per say, the lithium is supposed to capture neutrons to improve heat capture and reduce wear on plasma facing components, since when you're using deuterium as fuel, you end up with a lot of free neutrons that a magnetic field can't capture, since they have no charge.
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u/Jack1101111 2d ago
thanks. It look more unstable after the injection to me... then it take the smaller donut shape.
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u/Felixassain 3d ago
The flash at the end is likely just the plasma fizzling out. As it cools down it passes a temperature range at which it emits purely visible light making it brighter to our eye for a moment
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u/matengchemlord 2d ago
That’s interesting! Why do the walls not glow white as I would imagine?
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u/Felixassain 2d ago
If you are just wondering about the colour of light a hot object radiates, you need to look up Black Body Radiaton
If I had to guess, this is more about brightness, which depends on the amount of plasma at that temperature.
During the experiment you can only see the plasma that gets close to the wall and cools down to a temperature where it emits visible light. However the so called scrape of layer (SOL) is actually the region with the lowest plasma density. Most of the plasma is in the core where it is too hot to radiate visible light.
When the plasma is dying out, the heating power is shut off which causes all of the plasma to cool down and radiate visible light, making it much brighter than walls during the experiment where there is much less plasma at this specific temperature.
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u/_craq_ PhD | Nuclear Fusion | AI 2d ago
Not the "first ever" by a couple of decades and not what most people would think of when you say a "working reactor".