A spheromak is a magnetic fusion energy concept in which the plasma is in magnetohydrodynamic equilibrium. The stabilizing magnetic field is largely self-generated through plasma currents, leading to a stable, typically toroidal plasma; the term 'spheromak' is also used to refer to the plasma configuration itself.
A spheromak device is, like a Field-Reversed Configuration, considered a type of compact toroid. In contrast with tokamaks and stellarators, spheromak devices have relatively simple designs which require only one set of magnetic coils. Spheromak devices can be built somewhat like tokamaks, in a cylindrical structure, but the stability of spheromak plasmas also allows their creation by 'gun' devices. In a plasma gun, a pulse of electricity ionizes some gas, which is expelled from the barrel and coalesces into a stable spheromak. By colliding spheromaks together, scientists can study magnetic reconnection and other stellar phenomena.
The spheromak is an "alternate concept" that is considered by many plasma physicists to be less promising than the tokamak and stellarator (in terms of generating fusion energy), and accordingly receives relatively little attention and funding. General Fusion, a Canadian start-up enterprise, has published plans to develop a commercial fusion reactor based on the Spheromak technology as soon as there has been acquired sufficient starting capital (2009-08-03).
A spheromak plasma is often modelled as a Taylor state equilibrium, with the magnetic field satisfying the eigen value equation .