Improved Plasma Confinement at High Beta

A new efficient method of confinement is proposed for use in linear traps. The plasma equilibrium in a linear trap at high beta can evolve into a kind of diamagnetic bubble with a very small field inside. If the vacuum magnetic field of the trap has a quasi-uniform stretch near its minimum, the roughly cylindrical bubble with non-paraxial ends will occupy just this stretch. The bubble radius is determined by the balance of particle and energy fluxes, while the force balance corresponds to beta approximate to 1 at any radius. The effective mirror ratio of the trap in this diamagnetic regime can become very large, stifling the axial losses, but the cross-field transport inside it increases. The total confinement time can be found from solution of the system of equilibrium and transport equations and is shown to be tau(E) approximate to root tau(vertical bar vertical bar)tau(perpendicular to). This means that the diamagnetic confinement at high beta allows construction of relatively short linear traps as fusion reactors.