In December 2022, scientists at the US National Ignition Facility announced a historic milestone: for the first time, their laser-driven fusion reaction had “balanced out,” producing more energy than it consumed.
But breakthroughs as important as this must be rigorously monitored, and that can take some time.
Importantly, a series of papers detailing the experimental design, technological advances, and results of the initial breakthrough reaction have just passed peer review, meaning that researchers not involved in the work have examined the methods and findings to verify the sums.
“This achievement is the culmination of more than five decades of research and demonstrates that laboratory fusion, based on fundamental physical principles, is possible,” write team members of the Indirect Drive ICF (inertial confinement fusion) collaboration in the first of five documents.
Nuclear fusion, if harnessed and scaled up, promises an abundant and inexhaustible source of clean energy without the greenhouse gas emissions of fossil fuels or the radioactive waste of nuclear fission. Fusion is the fusion of two or more atoms to form a larger atom, releasing energy in the process.
These laboratory reactions are a far cry from commercial-scale applications, as they mimic the fusion reactions that power our Sun and stars on a small scale. Without the Sun’s mass to provide any gravitational grunt, methods for fusing atoms on Earth rely on heat.
In the case of this particular fusion technology, that heat is delivered through a powerful burst of light. The experiments involve bombarding a capsule containing a paltry 220 micrograms of deuterium-tritium fuel with 192 high-powered lasers, raising the pressure to 600 billion atmospheres and the temperature to 151 million °C (272 million °C). F).
These conditions, which far exceed those inside the Sun, cause the fuel to implode, the deuterium and tritium atoms fusing into helium and releasing energy.
In the groundbreaking December 2022 experiment, lasers fired 2.05 megajoules (MJ) of energy into the fuel, resulting in the release of 3.15 MJ, so the reaction produced about 1.5 times more energy than that delivered to the fuel.
The new papers detail the progress that made “balance” possible, including adjusting the fuel mixture, eliminating defects in the capsule walls, increasing the mass of the pea-sized capsule, increasing of laser energies and the increase in the volume of fuel used.
Passing that so-called ignition threshold heralded a new era in fusion research, which hasn’t slowed since: Researchers fired more energetic lasers and produced even more energy in several experiments last year.
The researchers also report results from one of those more recent experiments, from mid-2023, which generated 3.88 MJ of energy from the same 2.05 MJ energy input, about 1.9 times the energy injected. , which is the highest performance to date.
However, keep in mind that enormous amounts of energy are used to power the lasers in these experiments: 500 trillion watts, or a thousand times more energy than the US national energy grid produces at any given time. So there is a long way to go before these fusion reactions actually generate more energy than is needed to trigger them.
“There is a possibility that we will have fusion,” said Martin Freer, a nuclear physicist at the University of Birmingham. New scientists Matthew Sparks. “But the challenges we have are quite big, from a scientific point of view.”
Despite its promise of clean energy, scientists also emphasize that nuclear fusion is not the immediate solution we need to the climate crisis.
Commercial nuclear fusion facilities are still decades away, says University of Manchester nuclear fusion researcher Aneeqa Khan, when we need to almost halve global carbon emissions in the next six years (by 2030) to change the climate.
Fortunately, we already have the renewable energy technologies to do so.
The five articles have been published in Physical examination letters, which you can read here, here, here, here and here.