Lyman Spitzer with his Model A figure-eight stellarator. (Credit: Princeton Plasma Physics Laboratory)

The first concept of a stellarator in the shape of a three-dimensional figure eight. Model A was built in 1953 at the Princeton Plasma Physics Laboratory by Lyman Spitzer from a borosilicate glass tube. The shape of the figure-eight allows a so-called rotational transform to take place. The particle simultaneously orbits the axis of the tube as it travels through the stellarator. The particle is thus held on closed magnetic surfaces and confined by the magnetic field inside the stellarator. The concept of the three-dimensional figure-eight was used only in the first versions of stellarators and was then replaced by other concepts (classical, heliotron, heliac, modular, etc.).