Stellarator

A stellarator is a fusion power device that confines superheated plasma using only external magnetic coils, without relying on an electric current driven through the plasma itself, and takes its name from the stars, where fusion occurs naturally. Its coils are wound into a twisted, often figure-eight or racetrack-shaped toroidal geometry engineered specifically to counteract the plasma drift that would otherwise let confinement escape; because it carries no internal plasma current, a stellarator avoids the current-driven instabilities that affect a tokamak and is inherently suited to steady, continuous operation, though it requires more complex and powerful magnets to achieve comparable confinement. American physicist Lyman Spitzer invented the concept in 1951, reportedly while riding a ski lift, and built the first working device, Model A, at Princeton in 1953. Interest in the design faded after early tokamaks outperformed it but revived from the 1990s onward as tokamaks hit their own performance limits; Wendelstein 7-X in Germany and the Large Helical Device in Japan are the leading stellarators operating today, and private companies including Proxima Fusion and Type One Energy have since entered the field.