An early type of stellarator with an oval shape. The B-65 and B-66 models built at Princeton University in 1957 and 1959 were racetrack-shaped. They were a simplification of the figure-eight stellarator and a precursor to the classical stellarator. Helical coils were added to the curved portion of the stellarator, which improved the shape of the magnetic field, providing rotational transform and magnetic shear. Racetrack stellarators contained a divertor and experimented with ion cyclotron heating, which allowed them to reach temperatures up to 200 eV. However, due to strong particle drift, they did not achieve long enough confinement times.