Abstract
High poloidal beta (βp approximately 5) discharges produced with nearly balanced tangential neutral beam injection into low current discharges in the TFTR tokamak are described. As βp exceeds approximately 1.2 times the aspect ratio, a separatrix with an inside poloidal field null is observed to limit the outer boundary of the plasma. Since the curvature of TFTR's applied vertical field is constant, the appearance of the poloidal field null corresponds to the equilibrium poloidal beta limit