Stellarator

A stellarator is a fusion power device that confines plasma using external magnets. It is one of many types of magnetic confinement fusion devices, and among the first to be invented. The name "stellarator" refers to stars because fusion mostly occurs in stars such as the Sun. It is one of the earliest human-designed fusion power devices.

The stellarator was invented by American scientist Lyman Spitzer in 1951. Much of its early development was carried out by Spitzer's team at what became the Princeton Plasma Physics Laboratory (PPPL). Spitzer's Model A began operation in 1953 and demonstrated plasma confinement. Larger models followed, but demonstrated poor performance, losing plasma at rates far worse than theoretical predictions. By the early 1960s, attention turned to fundamental theory. By the mid-1960s, Spitzer was convinced that the stellarator was matching the Bohm diffusion rate, which suggested it would never be a practical fusion device.

The USSR's tokamak design augured a leap in performance. PPPL converted the Model C stellarator to the Symmetrical Tokamak (ST) to confirm or deny its results. ST surpassed them. Large-scale stellarator work in the US was replaced by tokamaks. Research continued in Germany and Japan, addressing many of the original problems, and began to approach the performance of early tokamaks.

The tokamak ultimately proved to have problems similar to the stellarators (for different reasons). Since the 1990s, stellarator interest rekindled. New techniques increased field quality and power, improving performance.