Dal Undergraduate Physics Society

Researchers at @TokamakEnergy have captured for the first time a real-time, high-speed video of plasma behaviour inside their ST40 spherical tokamak, tracking visible green and red light emissions as the fusion process occurs. This visual insight comes via a camera operating at thousands of frames per second, offering unprecedented detail of how the plasma evolves, interacts with the surrounding lithium blanket and outer regions, and ultimately radiates energy. The imaging enables scientists to observe how the ultra-hot core transitions outward into cooler zones, how magnetic confinement shapes the plasma behaviour, and how impurities or outer-region interactions influence the process. By giving a ‘star-in-a-donut’ view of fusion in action, this breakthrough adds a new diagnostic tool to the development of fusion energy, helping engineers refine the magnetic confinement, optimise plasma stability and better understand the heat and light flows at play. It was slowed down by 100x. All this was for 0.3s A tokamak is one of the most advanced devices ever created to achieve controlled nuclear fusion, the same process that powers the Sun. Its goal is simple in principle but incredibly challenging in practice: heat a gas until it becomes plasma, raise that plasma to over 100 million degrees, and confine it long enough for hydrogen nuclei to fuse and release energy. Because no material container can survive such temperatures, a tokamak uses powerful magnetic fields to hold and shape the plasma like an invisible cage. The device has a distinctive doughnut-shaped (toroidal) chamber surrounded by magnetic coils. When the machine is switched on, electric currents and external magnets work together to create helical magnetic fields that trap the plasma and keep it away from the walls. As the plasma spirals around these magnetic lines, it heats up dramatically. Additional heating comes from methods like radio-frequency waves and neutral-beam injection, pushing the plasma toward the extreme temperatures needed for fusion. Inside this tightly controlled environment, hydrogen isotopes such as deuterium and tritium can collide and fuse, releasing fast neutrons and a burst of energy. The goal of tokamak research is to reach a point where the fusion reactions produce more energy than the system consumes, a milestone known as “net energy gain.” Modern machines like ITER, JET, and Tokamak Energy’s ST40 are bringing this vision closer, using advanced diagnostics, superconducting magnets, and increasingly stable plasma control. 👉 tokamakenergy.com/2025/10/15…