A small-aspect-ratio torus for demonstrating thermonuclear ignition

A tokamak with 2.6-m major radius and aspect ratio of 2.0 is proposed for demonstrating thermonuclear ignition in deuterium-tritium. The 6-MA plasma current is established in part by co-injection only of 40MW of 80-keV neutral beams (inducing approximately 2MA at low density) and in part by the flux swing of the equilibrium-field system (inducing approximately 4MA as the plasma pressure is increased) - there is no central current transformer and no poloidal-field coils inboard of the plasma. The core of the device consists simply of a 1.9-m-diameter steel-reinforced conducting trunk formed by coalescence of the inner legs of the toroidal-field coils. With a tensile stress at the copper trunk of 1000kg/cm2, corresponding to 11T, the plasma density is sufficiently large to provide a comfortable safety margin for achieving ignition conditions. (author)