A self-contained plasma configuration with closed magnetic surfaces but no material linking the torus — including spheromaks and field-reversed configurations, attractive for their simplicity.
ReviewedLast reviewed: 9 Aug 2026·Category: Glossary
Definition
A compact toroid (CT) is a magnetically confined plasma configuration that forms a closed toroidal structure without requiring any material object (such as a centre column) passing through the “hole” of the torus. This makes compact toroids potentially simpler and cheaper than tokamaks or stellarators.[1]
Two main types: (1) Field-Reversed Configuration (FRC) — a compact toroid with no toroidal magnetic field, confined entirely by poloidal field generated by plasma currents. Very high beta (~1). (2) Spheromak — a compact toroid with both toroidal and poloidal fields, self-organized through relaxation. Moderate beta (~10–20%).
Physics
Compact toroids can be formed, translated (moved along a guide field), and compressed — properties that make them attractive for magneto-inertial fusion schemes. Their self-organized nature means they can be formed by simple pulsed circuits without complex shaping coils.[2]
Applications
TAE Technologies and Helion Energy pursue FRC-based fusion. General Fusion uses a CT as the target plasma for magnetized target fusion. CT injection has also been explored as a fueling method for tokamaks and as a means of driving current in other devices.[3]
Sources
Tuszewski, M. "Field reversed configurations." Nuclear Fusion, 28, 2033, 1988.
Bellan, P.M. Spheromaks: A Practical Application of Magnetohydrodynamic Dynamos and Plasma Self-Organization. Imperial College Press, 2000.
Fusion Industry Association. "The Global Fusion Industry in 2024." FIA Annual Survey, 2024.