Fusion For the First Time: Harnessing the Energy of Stars
Issue 9, Volume 113
Every day, the Sun’s immense heat warms our planet and provides the energy needed for life to exist on Earth. This heat comes from the Sun’s core, where extreme temperatures and pressure cause atoms to fuse and release energy. What if humans could recreate this process? How would it look? Perhaps something like this: 192 laser beams bombarding a fuel capsule the size of a pencil eraser. For a few billionths of a second, the temperature surpasses three million degrees Celsius, creating the same fusion process found in the cores of stars. At the National Ignition Facility (NIF), scientists have done just that, bringing humanity one step closer to harnessing fusion energy.
The basis of nuclear fusion is that atomic nuclei hold enormous amounts of energy. When atoms fuse, they release a fraction of their nuclear potential energy as heat. The generation of this energy does not emit carbon dioxide or highly radioactive wastes the way that the combustion of fossil fuels and the generation of energy through nuclear fission power plants do. However, the atoms must overcome the overwhelming repellant forces between their nuclei to begin fusing. That is, they must pass the bounds of the strong nuclear force. While the cores of stars like the Sun are naturally subject to high pressures and temperatures that facilitate the fusion process, it is significantly more difficult to recreate these conditions on Earth. At Earth’s standard air pressure, fusion would require temperatures of at least 100 million degrees Celsius, seven times the temperature of the Sun’s core.
Despite this, the United States Department of Energy announced on December 13, 2022, that the NIF had completed its first controlled experiment to reach fusion ignition. In other words, for the first time, a fusion reaction produced more energy than inputted. The fuel mixture absorbed 2.05 megajoules of energy to release 3.15 megajoules. This incredible milestone represents an energy gain factor of over 1.5, meaning the reaction produced 50 percent more energy than the input. The NIF’s previous record was 1.3 megajoules.
The NIF is an inertial confinement system, which rapidly compresses hydrogen fuel to produce a quick but powerful burst of energy rather than a prolonged reaction. It is, in essence, an explosion; the most destructive weapon humans have developed, the Tsar Bomba, utilizes the same principle. The NIF consists of a massive laser system the size of a sports stadium and a central reaction chamber known as the “hohlraum.” The fusion fuel cell, a carefully engineered diamond capsule inside a gold canister, sits at the center of the hohlraum. The capsule is less than a centimeter wide, and about 10 milligrams of hydrogen fuel are frozen inside it.
Initially, the system creates a single infrared laser beam. The massive laser system multiplies and amplifies this original beam into 192 high-powered beams of ultraviolet light. These laser beams are directed to the central chamber and collide simultaneously with the canister. Their energy heats the can to over three million degrees Celsius, causing it to emit high-energy X-rays. These X-rays penetrate and vaporize the inner diamond layer, generating massive pressure on the hydrogen atoms. The combined pressure and temperature are enough to force the atoms to fuse. Nanoseconds later, the pressure dissipates, and the fusion ends. The entire process completes in less than a second.
For the first time, the initial energy input sustained a fusion reaction that could provide its own energy. Scientists successfully generated a net energy gain with fusion reactions, which no other experiment had succeeded with before. Now that scientists know how to achieve fusion ignition, they can continue to repeat it and study its mechanics. The collective work of engineers and scientists over many decades has led up to this moment, and this experiment is a breakthrough point in the development of fusion reactors.
But even with the phenomenal bounds made by this breakthrough, there are a few caveats. For one, the NIF experiment does not represent a viable way to generate energy. Though the reaction produced three megajoules of energy, the system used 322 megajoules of electricity altogether. As noted before, the NIF’s system only creates a burst of energy, which is not sustainable for generating electricity. Though laser systems are not likely to be used in future fusion facilities, the NIF experiment has brought humans closer to harnessing its power than ever before.
Human recreation of the abundant clean energy of stars would have substantial implications. Fusion energy uses readily available hydrogen fuel, does not produce dangerous byproducts, and does not lead to runaway meltdowns. This clean, powerful source of energy can end humanity’s dependence on fossil fuels to power every appliance, heating system, or factory in the world. It’s not hard to imagine that, in a few decades, the same process that powers the Sun may just power everything in your life.