Self-sustaining plasma toroid, similar to a smoke ring, with relatively long confinement times of about a microsecond. An internal electric current flows through the spheromak, generating a magnetic field that stabilizes it. Spheromaks are relatively easy to create. For example, by using a Marshall gun, where a pair of nested cylinders create a magnetic field shaped to form the ionised gas into a spheromak. They are widely used for the study of astrophysical events, but they are also explored as possible ways to achieve fusion.