Inertial Fusion Energy (IFE)

Small, spherical plastic capsules are filled to a high pressure with a mixture of Deuterium and Tritium, in equal parts. They are then chilled so that a thin, frozen coating of the mixture develops on the inside of the capsule. The capsule is usually, but not necessarily, put inside a metal container called a hohlraum, shown to the right.

Altered image from (link)

Pulses from lasers or high-energy ion beams, which are also called the "driver," heat the capsule, so that its surface vaporizes into a plasma. As this plasma expands outward, the frozen D-T coating is forced inward by the laws of physics, further compressing the remaining D-T gas to pressures of hundreds of millions of atmospheres. The gas temperature will reach above 100 million degrees Celcius. The gas then ignites as the Deuterium and Tritium atoms fuse and a "burn wave" is created, which spreads outward to the denser once-frozen D-T layer. This process is illustrated below:

Image courtesy of (link)

Current Status

Ignition and the creation of a burn wave in IFE experiments has not yet been achieved, and experiments in the near future (goal date: 2010) are predicted to generate only one-twentieth of the energy that was used to run the experiment. In order to be profitable, the fusion yield will have to reach about ten times the energy input. Laser, or driver, technology is the major impediment to this goal, whose realization is still many years away. [1]

Future Research Directions

There are several new areas of laser research being developed. The one receiving the most support from Congress and the D.O.E. is a heavy-ion driver. This driver uses induction acceleration to create dense beams of heavy ions, as opposed to radio-frequency acceleration of photons, which is currently being used in laser drivers. It can handle much higher currents and has the potential to be at least three times as efficient as laser drivers. Other promising research ideas are fast ignition and the use of a light ion driver. Fast ignition could greatly increase driver efficiency by first using a traditional laser pulse to compress the plasma, and then another, extremely short pulse of high current from a different laser to cause ignition. A light ion driver would use high currents of lighter ions such as Lithium.

Picture of a heavy ion driver. Image courtesy of (link)

Next, learn about magnetic confinement, or go on to other technical challenges:
Theoretical Research or Cold Fusion.

Sources

[1]. Yield data from personal communication with the National Ignition Facility, Lawrence Livermore National Laboratory, April 25, 2002.