Fusion is the combination of two light nuclei such as hydrogen or helium to form a heavier element and in the process, releasing large amounts of energy. This might be harnessed to produce useful electric power. Although there are several areas of fusion research, the leading development path goes straight into the land of plasma physics.

When most people hear the word plasma they think of the local blood bank, however, within the context of fusion a plasma is an ionized gas. That means that a gas has been heated to such an extent that the atoms have enough energy to separate into a fluid of ions and electrons, charged particles.

To obtain fusion the ions need to be hot enough and held together long enough. They need to have sufficient thermal energy to overcome their like-charge repulsion force and be contained for a certain amount of time to allow a fusion collision to take place.

As we all have observed, gases like to fill the volume of their container. Plasmas are no exception, but the incredible temperatures of fusion plasmas make it impossible to confine with any material wall. Scientists thought about how to make a container that could possibly hold a 100,000,000 C substance. They look at the sun and other stars for ideas.

Stars use gravity to balance the kinetic pressure or expanding force of the plasma. The gravity is supplied by the mass of the star itself.

Here on earth we don't have the option of using gravity, but since a plasma is a collection of charged particles electromagnetic forces may be used instead. It is possible to create a magnetic container to hold the plasma, this forms an equilibrium between the kinetic pressure and the magnetic pressure.

Various magnetic confinement ideas

• tokamak