A tokamak is a donut-shaped fusion device that uses powerful magnetic fields to confine a plasma hot enough for hydrogen nuclei to fuse and release energy — the most scientifically validated approach to recreating the process that powers the sun.
First developed in the Soviet Union in the 1950s, the tokamak confines charged particles in a toroidal chamber using a combination of external magnet coils and a current driven through the plasma itself. Because fusion requires temperatures above 100 million degrees Celsius, no material wall can hold the fuel; magnetic fields do the holding instead. Decades of experiments across hundreds of tokamaks — from the Joint European Torus to the international ITER project — built the performance database that makes tokamak physics the best understood in fusion science.
The central design lever is magnetic field strength: fusion power density scales steeply with field, so stronger magnets allow a smaller, cheaper machine to reach the same performance. That relationship is what 📝high-temperature superconducting (HTS) magnets changed — enabling compact, high-field tokamaks that pursue net energy in devices a fraction of ITER's size.