Acceleration of compact toroidal plasmas (or CT) is a synthesis of two well-developed concepts: the spheromak plasma configuration and the railgun accelerator. The spheromak compact toroid is a structure of plasma containing embedded toroidal and poloidal magnetic fields with associated poloidal and toroidal currents (Figure 1).
This provides a magnetic “bottle” that contains plasma. This plasma structure is a self-contained system with negligible net charge and a dipole magnetic moment. The plasma is typically confined on a time scale of several hundred microseconds and decays principally by energy loss to photon radiation driven by resistive dissipation of the plasma currents.
The railgun is a device that switches stored electrical energy from a capacitor bank into two rails with a moving projectile acting as an armature providing a conduction path between the rails. This creates a variable-inductance line with expanding stored magnetic flux pushing the projectile and accelerating it (Figure 2).
The unique feature of a CT accelerator is that the armature-projectile in the railgun is that self-contained structure of plasma, the compact toroid (Figure 3).