Seeing the inside of a nuclear fusion reactor is, for obvious reasons, complicated. We are talking about temperatures of millions of degrees Celsius, hotter than the core of the Sun. However, the British company Tokamak Energy has just given us unprecedented images of what is happening inside its ST40 spherical reactor: a video in full color and at the incredible speed of 16,000 frames per second.
An unprecedented ballet of colors. What we are seeing in the video is, in essence, the choreography of the elements within the tokamak. The ST40, like most of these reactors, uses hydrogen isotopes (deuterium in this case) as fuel. When this gas turns into plasma, it emits a characteristic pink light, which dominates the scene. But the interesting part begins when researchers introduce lithium, which glows red.
And no, this is not just a visual spectacle. Every color, every bright filament we see in these images, is a gold mine of information that is helping scientists solve one of the biggest challenges on the long road to commercial fusion energy: how to tame plasma so that it does not degrade reactor materials.
What exactly are we seeing? In the images, we see how small granules of lithium are injected into the reactor chamber. Upon entering the outer, colder areas of the plasma, the neutral lithium is excited and emits an intense crimson red light. As they penetrate the hottest and densest regions, lithium atoms lose an electron, become ionized (becoming lithium ions), and begin to glow greenish.
Once ionized, lithium no longer moves freely. It is forced to follow the invisible, but very powerful magnetic field lines that confine the plasma. Those green filaments that we see dancing in the video are, literally, the lithium drawing the magnetic cage of the reactor.
What is all this for? The lithium acts as a protective shield for the reactor. Recording what happens in color is not easy, but it helps identify whether the impurities that Totakak Energy is introducing into the reactor radiate in the expected place. And if the lithium powders penetrate to the core of the plasma.
This experiment is part of research into a mode of operation called the “X-point radiator” (XPR) that uses elements such as lithium so that the edge of the plasma radiates and loses a large amount of heat before touching the reactor walls. It is a protective “atmosphere” that cools the plasma just at the last moment, reducing component wear without sacrificing core performance.
The advancement of Tokamak Energy. This approach is the centerpiece of the Dell ST40 upgrade program, which has received funding from the US and UK energy departments. The goal is to coat all the components that face the plasma with lithium, a technique that has already been demonstrated in other laboratories, such as Princeton, to improve plasma performance.
This type of visual diagnostics complement the incredibly complex systems that are being installed in reactors such as the JT-60SA in Japan, the most advanced tokamak in the world currentlywhich uses lasers to measure plasma temperature and density indirectly.
A global career. While colossal and institutional projects such as ITER They mark a long-term pathwhich plans its first deuterium-tritium experiments by 2039, more agile companies like Tokamak Energy are exploring new designs and technologies, such as spherical tokamaks and high-temperature superconducting magnets, to accelerate the arrival of commercial fusion.
The closure of the historic JET reactor in the United Kingdom, who said goodbye breaking an energy recordmarked the end of an era, but its legacy is the foundation on which all these new advances are built. This new window into the heart of plasma is not only visually impressive. It is a small step that brings us a little closer to the goal of replicating the energy of stars on Earth. Nuclear fusion just got a lot more colorful, and that’s great news.
Image | Tokamak Energy
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