Reversed field pinch, compact toroids, and dense Z-pinch

The tokamak is the primary plasma confinement device, under development around the world, as a source for magnetic fusion energy. The reversed field pinch, compact toroids, and dense Z-pinch are frequently referred to as 'alternates', meaning that they are different from the tokamak but candidates, ultimately, as confinement devices for energy-producing plasma. These alternates are of interest in some cases because they offer potential advantages in a reactor embodiment (e.g., reduced magnetic field requirements). In other cases, the interest to the national program is primarily because of some specialized application, such as the potential of the Z-pinch as a neutron source. In all cases, the plasma physics insights gained through study of these devices will be important to the evaluation of plasma fusion broadly. In fact, the different view of the same fundamental physics when applied in tokamaks can provide insights and advances that prove to be critical for tokamak advancement.