What is a Compact Torus?

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).


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