Tokamak:

Magnetic Confinment Chamber

Fusion can be created in three different ways: gravitational confinement, magnetic confinement, and inertial confinement. Gravitational confinement is witnessed every day when we look up at the sun. Since the sun is so massive the gravity at its core is powerful enough to squeeze hydrogen atoms together to form helium atoms. Though this is an efficient method for stars, earths' gravity is insufficient to create fusion. The other two possibilities, magnetic and inertial confinements, are possible, and research is being focused in those areas.

In magnetic confinements a tokamak chamber has yielded the best results. A tokamak is "a toroidal device comprising a hollow doughnut-shaped vessel through which magnetic fields twists [;] it is the most common magnetic confinement device understudy" (Fusion: Energy Source 1). The basic idea behind the tokamak is to confine the plasma in a chamber and extract thermal energy through the fusion reaction. Since plasma is electrically charged it can essentially float through the chamber without touching the walls. This enables the plasma reaction to reach "temperatures in excess of 100,000,000 degrees centigrade (the temperature of the sun) [while staying] confined inside a metal chamber whose surface is nearer room temperature" (Glanz 7). While the temperature of the plasma is very high its density is very low; the density in the chamber is "lower than atmospheric density"(1216 Physics). With the density being so low the plasma acts like the steam in the pot of hot water. The reason the plasma can have such a low density and still create fusion is because of the long confinement times in side the chamber, sometimes reaching up to several seconds in some devices.