Magnetic Confinement Fusion
The more popular method of creating a controlled fusion reactor relies on the principle of magnetic confinement. At the temperatures necessary to initiate and maintain fusion (in the range of 100 million degrees Celsius) the hydrogen exist in a plasma state, and cannot be contained by known materials. Magnetic confinement, however, utilizes the fact that plasma consists of charged ions, and a correctly aligned, strong magnetic field can confine the plasma and keep it away from the chamber walls. This method is used to "contain the plasma for a long time at a low density.[1] "
Several attempts are currently being made in the attainment of a commercially viable fusion power plant. One such attempt is the tokamak design ("Torroidal Chamber and Magnetic Coil"). This design employs a main chamber in a doughnut, or torroidal, shape. The chamber is wrapped with coils in which current is flowing, generating a magnetic field stronger towards the center that forces the plasma away, towards the walls. However, a second magnetic field is made possible by the current flowing through the plasma itself, creating field lines that spiral around the torus, trapping the plasma.[1]
Figure 1 - depiction of toroidal magnetic confinement chamber