Plasma Behavior in a Toroidal High‐β Device

The stability of a cusp magnetic field has been combined with the low loss rate of a closed field configuration in a series of three small toroidal devices designed for plasma containment. In operation, a pinch partly stabilized by an axial magnetic field, is produced prior to application of the containing cusp field. The axial stabilizing field of the pinch is then trapped by the plasma so that closed field lines are maintained within the plasma while the cusp is excluded from the plasma. There is no evidence of turbulence and the device exhibits a loss rate an order of magnitude below that to be expected from the same device operated as a minimum‐B configuration without field trapping. Containment time is dependent on the decay rate of the applied cusp field. Maximum value of β within the plasma exceeds 2 and β remains above 1 for 15 μsec. Electron densities and temperatures exceed 1016 cm−3 and 105 °K, respectively.