Features of spherical torus plasmas

The spherical torus is a very small aspect ratio (A 2 are characterized by high toroidal beta (βt > 0.2), low poloidal beta (βp 1.5), and strong magnetic helical pitch (Θ comparable to F). A large near-omnigeneous region is seen in the large major radius, bad curvature region of the plasma in comparison with the conventional tokamaks. These features combine to engender the spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost. Because of its strong paramagnetism and helical pitch, the spherical torus plasma shares some of the desirable features of spheromak and reversed-field pinch (RFP) plasmas, but with tokamak-like confinement and safety factor q. The general class of spherical tori, which includes the spherical tokamak (q>1), the spherical pinch (1>q>0), and the spherical RFP (q<0), have magnetic field configurations unique in comparison with conventional tokamaks and RFPs.

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