 However, it was found that formula_6 changed dramatically with the shape of the plasma, and non-circular systems would have much better performance.Experiments on the DIII-D machine (the second D referring to the cross-sectional shape of the plasma) demonstrated higher performance, and the spherical tokamak design outperformed the Troyon limit by about 10 times.Beta is also sometimes used when discussing the interaction of plasma in space with different magnetic fields.