Methods of Confinement

Because plasma temperatures of at least 100 million degrees Centigrade are needed to initiate fusion reactions, confinement of the plasma is a major challenge. Two separate methods of confinement have been developed: magnetic and inertial. Each method has different obstacles to its success as an energy source.

In order to reach ignition, and thus viability, in a fusion reactor, a criteria known as the Lawson triple product must be met. For a density n, temperature T and confinement time t, this criteria states that:

n*T*t > 5 x 10^21 m-3 s keV

Currently, magnetic confinement devices have attained a triple product as high as 8.3 x 10^20 m-3 s keV, about a factor of 6 less than what is needed. However through the past 30-40 years there has been a near exponential increase in the achieved triple product, leading to the expectation that the fusion break-even point will be achieved soon.