Scientists hoping to harness nuclear fusion—the same energy source that powers the Sun and other stars—have confirmed that magnetic fields can enhance the energy output of their experiments, reports a new study.
The results suggest that magnets may play a key role in the development of this futuristic form of power, which could theoretically provide a virtually limitless supply of clean energy. While this is an exciting prospect, most experts believe that it will take decades to engineer a working fusion reactor, assuming it is possible at all.
Fusion power is generated by the immense energy released as atoms in extreme environments merge together to create new configurations. The Sun, and all the stars in the night sky, are fueled by this explosive process, which occurs in their cores at incredibly high temperatures and pressures. Scientists have spent roughly a century unraveling the mechanics of nuclear fusion in nature, and trying to artificially replicate this starry mojo in laboratories.
Now, a team at the National Ignition Facility (NIF), which is a fusion experiment based at the U.S. Department of Energy’s Lawrence Livermore National Laboratory, has reported that the magnetic fields can boost the temperature of the fusion “hot spot” in experiments by 40 percent and more than triple its energy output, which is “approaching what is required for fusion ignition” according to a study published this month in Physical Review Letters.
“The magnetic field comes in and acts kind of like an insulator,” said John Moody, a senior scientist at the NIF who led the study, in a call with Motherboard. “You have what we call the hot spot. It’s millions of degrees, and around it is just room temperature. All that heat wants to flow out because heat always goes from the hot to the cold and the magnetic field prevents that from happening.”
“When we go in and we put the magnetic field on this hotspot, and we insulate it, now that heat stays in there, and so we're able to get the hot spot to a higher temperature,” he continued. “You get more [fusion] reactions as you go up in temperature, and that's why we see this improvement in the reactivity.”
The hot spots in the NIF’s fusion experiments are created by shooting nearly 200 lasers at a tiny pellet of fuel made of heavier isotopes (or versions) of hydrogen, such as deuterium and tritium. These laser blasts generate X-rays that make the small capsule implode, producing the kinds of extreme pressures and temperatures that are necessary for the isotopes to fuse together and release their enormous stores of energy.
NIF has already brought their experiments to the brink of ignition, which is the point at which fusion reactions become self-sustaining in plasmas. The energy yields created by these experiments are completely outweighed by the energy that it takes to make these self-sustaining reactions in the plasmas in the first place. Still, achieving ignition is an important step toward creating a possible “breakeven” system that produces more energy output than input.
Fusion experiments are so complex that even the most minor changes to their setups can have big repercussions. With that in mind, Moody and his colleagues developed their magnetized experiment at NIF by wrapping a coil around a version of the pellet made with specialized metals.
The research follows a 2012 experiment at the OMEGA facility at the University of Rochester, which found that magnets can increase the temperature of fusion fuel. However, the NIF team was able to create the biggest temperature and energy increase ever achieved with a magnetized fusion experiment because of their unique experimental setup. The hot spot at NIF was 40 percent hotter, and produced more than three times the energetic yield, compared to previous experiments, a result that was even better than predictions.
The researchers plan to conduct more fusion experiments with magnetic fields, including a version with an ice-covered cryogenic fuel capsule, to better understand the mysterious physics at work in these extreme systems.
“The fact that we saw a greater improvement in the yield [than predicted] was actually kind of surprising,” Moody said. “We're still trying to understand why. Anytime there's a difference between the experiment and the theory, there's a lot you can learn by trying to figure out what happened.
“Is it because there are unexpected things that happened that are good, and those things will carry over when we do the ice-layered implosion?” he added. “I'd like to think that but it doesn't really matter what I'd like to think. What is the reality?”
Indeed, magnets are one cog in an incredibly complicated machine and it will take many more years to assess their potential role in fusion power. The advances at NIF, and at other fusion experiments around the world, can at times seem painstakingly incremental, but this slow progress may have an incalculable payoff down the line, which is a dream that is, like fusion reaction plasmas, self-sustaining.
To that end, future experiments at NIF will help scientists assess how magnets could potentially enhance the efficiency of fusion reactions, while also opening a new window into a host of unanswered scientific questions.
“We could do some really interesting studies where you can generate really high magnetic fields in these hotspots, so we might do some never-done-before science experiments in the laboratory,” Moody concluded.