Overview of stoppering of open magnetic containment systems for controlled fusion

Magnetic confinement systems with the field lines leading out of the system are subject to end loss. The rate of end loss must be reduced to a sufficiently small value in a reactor such that fusion energy is generated more rapidly than energy is lost. The basic open ended systems either have too high an end loss to satisfy the reactor criterion (single mirrors and cusps), or are too long to be considered practical (long solenoids). Various end stopping schemes were proposed to reduce the end loss of open ended systems, and thus make the energy balance more favorable. The end stoppering techniques were electrostatic, RF, magnetic, material walls, and hybrid systems. The more important characteristics and the potentialities of the first three methods of end stoppering are summarized.