Physicists report first creation of self-heating plasma for nuclear fusion
Nuclear physicists are notching scientific advances for fusion energy, fueling hopes — and billions in investment — to create an energy source that doesn't produce carbon or long-living nuclear waste.
Why it matters: For decades, scientists have chased the dream of using fusion for limitless clean energy. But turning the science into a commercial technology still faces scientific, technical and financial hurdles.
The goal is to build a machine that can control nuclear fusion reactions — when the nuclei of two light atoms combine to create the nucleus of a heavier atom and generate energy in the process.
- Crucially, the reactors would have to produce more energy than they require in the first place to achieve fusion.
- Researchers have tried for decades to mimic massive fusion reactions seen in stars like our Sun on a smaller scale here on Earth. They've focused on combining nuclei of deuterium and tritium, both of which are isotopes or versions of hydrogen, to create a helium nucleus — and capturing the energy released.
- The extremely hot plasma (about 100 million degrees Celsius) in which fusion reactions occur can be contained using powerful magnetic fields or by compressing the fuel using lasers or beams of particles.
- But it requires feeding the reaction a lot of energy.
Driving the news: Researchers at the Lawrence Livermore National Laboratory's National Ignition Facility (NIF) this week reported creating a self-heating plasma for the first time in a laboratory.
- A self-heating plasma is significant because "fusion is now providing the majority of the heating," says Alex Zylstra, an experimental physicist at LLNL and an author of the study published this week in Nature.
- That's a key prerequisite step for getting large amounts of energy out of the fuel with their laser-fusion approach.
- The next major milestone to reach is ignition, Zylstra says. That's when the fuel can keep burning on its own and the energy output from the reactions is greater than what is required for starting fusion reactions in the first place.
How they did it: NIF uses a deuterium and tritium fuel inside a polished diamond spherical capsule that is placed in a hollow container.
- 192 lasers pointed at the container produce X-rays that rapidly heat and expand the capsule, compressing the fuel to pressures greater than those in the Sun to start the fusion reactions.
- In experiments performed in late 2020 and early 2021, researchers were able to generate up to 170 kilojoules of energy — equivalent to about nine 9-volt batteries.
Yes, but: It still took roughly 10 times as much energy overall to operate the laser and create the reaction.
- In follow-up experiments in August 2021 that haven't yet been published, NIF scientists produced eight times as much energy but still short of the 1.9 megajoules of energy that goes into the reaction.
- But "it remains unclear whether this research will lead to a viable future power source," Nigel Woolsey, a professor of physics at the University of York who wasn't involved in the research, writes in an article accompanying the new paper.
- One challenge is that laser-fusion reactors operate for shorter periods of time than magnetic-fusion devices.
- NIF's laser-fusion experiments could yield insights into the basic physics of self-heated plasma, which are used in other fusion energy approaches, and how it behaves inside stars and nuclear weapons, which the facility is specifically designed to study.
- There are more than 40 private fusion companies globally, which have raised over $2.5 billion in investment to date, according to a report from the U.K. government.
- Some scientists claim they will be able to deliver fusion energy technology within a decade. Others say it will be another 50 years.
Where it stands: These are all still experiments, Woolsey and Zylstra tell Axios.
What to watch: To move from experiments to commercial technologies, fusion energy projects still face a number of hurdles, including engineering materials and structures that can withstand the harsh environment required for fusion over the lifetime of a reactor, Woolsey tells Axios.
- There is also the challenge of producing tritium, which some scientists propose could be bred around the fusion reactor.
- And, of course, a reactor still has to make more energy than it consumes to drive it.
Editor's note: This story has been updated to clarify that the process of nuclear fusion does not generate nuclear waste but the plants may become radioactive and produce small amounts of short-lived nuclear waste.