What is inertial fusion energy?

Everybody is talking about stopping fossil fuel energy production these days because of global warming. Then there are several alternatives. One of those is Fusion Energy. 

Fusion is a natural phenomenon that provides our planet with much of its energy—generated millions of miles away in the center of our sun.

Here on Earth, scientists are trying to replicate the hot and dense conditions that lead to fusion. In the center of a star, gravitational pressures and high temperatures—around 200 million degrees Fahrenheit—energize and squeeze atoms close enough together to fuse their nuclei and generate excess energy.

The end goal of fusion research is to reproduce a process that happens in stars all the time. Two light atoms come together and fuse to form a single heavier, more stable nucleus. As a result, excess mass—the one nucleus has less mass than the two that formed it—is converted to energy and carried away.

That leftover mass (m) becomes energy (E) thanks to Einstein's famous E=mc² equation. Getting fusion to happen on Earth is surprisingly simple—and has been achieved many times over the past few decades using a wide range of devices. The hard part is to make the process self-sustaining, so that one fusion event drives the next to create a sustained, "burning plasma" that could ultimately generate clean, safe and abundant energy to power the electric grid.

You can think of this like the striking of a match. Once ignited, the flame keeps burning. On Earth we have to create the right conditions—very high density and temperature—to get the process to happen, and one of the ways to do that is with lasers.

Enter inertial fusion energy, or IFE, a potential approach to building a commercial fusion power plant using fusion fuel and lasers. IFE has garnered increased support when scientists have repeatedly demonstrated fusion reactions that produced a net energy gain for the first time  in the world. With intense laser beams, scientists achieved ignition, which means they got more energy out of a fusion target than the  laser energy put into it.

The technique , known as inertial confinement fusion, is one of two primary ideas being explored for the creation of a fusion energy source. The other, known as magnetic confinement fusion, uses magnetic fields to contain fusion fuel in the form of plasma.

With inertial confinement fusion,  the plasma is created using intense lasers and a small pellet filled with hydrogen—typically deuterium and tritium, isotopes with one and two neutrons in the nucleus, respectively. The pellet is surrounded with a light material that vaporizes outwards when heated by the lasers. And when it does, there is a net reaction inward, driving an implosion.

This works like a rocket. The vaporized material on the outside of the pellet pushes the hydrogen isotopes in toward the center.

The lasers must be applied accurately to get a symmetrical shock wave moving toward the center of the hydrogen mixture—creating the temperature and density needed to start the fusion reaction. NIF ignition events use 192 laser beams to create this implosion and cause the isotopes to fuse.

Laser technology and our understanding of the fusion process has advanced so rapidly that we are now able to use laser confinement to create a burning plasma from each fusion event.

However, lasers used for inertial fusion energy must be able to fire more rapidly and become more electrically efficient, the experts say.

The lasers at NIF are so large and complex that they can only fire about three times a day. To reach an inertial fusion energy power source, we need lasers that can operate 10 times per second. So, we need to merge the NIF fusion results with efficient laser and fuel target technologies.

The potential for a clean, equitable and abundant energy source—and all the science and technology that comes alongside fusion energy development—is very exciting.