What is Inertial Confinement Fusion?

Michael Anissimov
Michael Anissimov

Inertial confinement fusion (ICF) is a method of achieving nuclear fusion by quickly compressing and heating a material. This process is usually done with high-powered lasers, which are all focused onto a small pellet to rapidly heat it up. The intense heating vaporizes the material inside the pellet, creating a shock wave which is hot and dense enough to cause the material to fuse. Although inertial confinement fusion has yet to produce more useful energy than it consumes, research on how to build a commercially viable power source is still in progress.

The ability to effectively confine a fusion reaction is key, because they occur at very high temperatures.
The ability to effectively confine a fusion reaction is key, because they occur at very high temperatures.

The basic ingredients of an inertial confinement fusion pellet are deuterium and tritium, both hydrogen isotopes. The fusion reaction between deuterium and tritium is much easier to achieve than any other reaction, and so a power-producing deuterium/tritium reactor is the primary goal of modern fusion research. These pellets are very small, weighing much less than a gram, and are inserted one at a time into the inertial confinement fusion reactor.

Once the pellet is loaded, very large lasers are used to rapidly heat the pellet up to fusion temperature, at millions of degrees Fahrenheit (Celsius). The rapid heating of the outer layer of the pellet causes it to vaporize and rapidly expand, putting pressure on the interior of the pellet. If the lasers supply enough energy, the interior of the pellet will be compressed quickly enough to induce nuclear fusion, which in turn makes the pellet hotter. This condition is called "ignition," and it is the goal of most modern-day inertial confinement fusion experiments.

The primary difficulty with inertial confinement fusion is delivering enough power to the pellet to heat it to fusion temperature before the pellet disperses into space. In order to produce power from fusion, the reaction must exceed a value called the Lawson criterion, which gives the minimum confinement time necessary for any given volume of fuel. This requires many megajoules of energy to be passed through the laser system in a matter of microseconds; doing this reliably, without consuming too much power, presents a huge technical challenge. A new approach to the confinement problem called "fast ignition" has been proposed, where a single quick laser burst ignites the pellet after it has already been compressed. Although this approach looks promising in theory, it has not yet been successfully tested.

Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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Discussion Comments


Laser fusion is exciting, but Heavy Ion Fusion - driving the pellet with a beam of ions from a particle accelerator instead of a laser - is much more exciting because it works better (more energy, more efficiency, higher rep rate) and could actually produce economical power. But Livermore (NIF) doesn't care about that, because they love lasers, and because their military sponsors don't actually care about energy production.


GeminiMama- I was totally thinking the same thing as I was reading this article. I am working on a project for one of my classes at a community college and have been reading for hours. But about halfway through reading this I began to play out the scene in my mind! Who says studying fusion can’t be fun.


GeminiMama- That is amazing your son is so inquisitive at such a young age. I think I was still into G.I. Joe’s at ten years old; but then again I didn’t have the awesome special effects that are now standard in today’s movies. I think it’s great he has a mom who could actually think of a way to show him the cool side of science, especially at a level he can understand.


My 10 year old son asked me what nuclear fusion was and we decided to look it up on here together. After reading this article to him aloud he wanted a visual because it sounds so cool.

The only thing I could do was to put on the scene in ‘Spiderman 3’ where Doc Oc attempts to achieve this theory at the end of the movie. So we watched the scene as I read off parts of this article again. Thank you wiseGeek!

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