A science institute in the United States is about to make a breakthrough in nuclear fusion research.
The National Ignition Facility (NIF) in Livermore, Calif., uses a powerful laser to heat and compress hydrogen fuel and is one step closer to achieving nuclear fusion of massive proportions.
From an experiment carried out in August 2021, the laboratory will soon reach the goal of “ignition”, when the energy released by the fusion will exceed that released by the laser.
Fusion is a type of nuclear energy that is different from the fission process, which has been used since 1950 in atomic energy reactors. In fusion, energy is generated from the union of atoms, while in fission it is a by-product of the splitting of atoms.
Fusion is the same process that takes place in the Sun, and it requires extreme heat and pressure and is much more difficult to control than fission. Once mastered, however, it could provide us with a source of clean and unlimited energy.
The process does not generate the radioactive waste produced by fission reactors, which is one of the main obstacles to the use of nuclear energy today, in addition to the cost and concern that the modality generates regarding the safety and proliferation of weapons.
In a process called nuclear fusion with inertial confinement, 192 laser beams from the NIF facility — the world’s highest concentration of energy — are aimed at a capsule the size of a peppercorn.
This capsule contains deuterium and tritium, which are different forms of the element hydrogen.
The procedure compresses the fuel to 100 times the density of lead and heats it to 100 million degrees Celsius — hotter than the center of the sun. These conditions help initiate thermonuclear fusion.
An experiment conducted on Aug. 8 yielded 1.35 megajoules (MJ) of energy — about 70% of the laser energy that reaches the fuel capsule. Achieving ignition means obtaining a fusion efficiency greater than the 1.9 MJ applied by the laser.
“This is a huge step forward for fusion research and for the entire community involved in it,” Debbie Callahan, a physicist at the Lawrence Livermore National Laboratory, which houses the NIF, told BBC News.
This month’s experiment achieved a result eight times higher than the previous record (earlier this year) and 25 times the throughput of experiments performed in 2018.
“The pace of advances in energy production has been rapid, suggesting that we may soon reach more records, such as surpassing the energy of lasers that initiate the process,” said Jeremy Chittenden, co-director of the Center for Studies in Inertial Fusion at Imperial College London , in England.
NIF scientists also believe they have achieved something called “burning plasma,” where the fusion reactions themselves give heat to further fusion. This is vital to making the process self-sustaining and high throughput.
“We believe our experiment has reached this stage, but we are still doing analysis and simulations to make sure we understand the result,” explains Debbie Callahan.
Afterwards, the tests will be performed again.
“This is fundamental to experimental science. We need to understand how reproducible the results are, and how sensitive they are to small changes,” says Callahn.
“Then we have plans to improve the design of this system. We will start working on it next year.”
Despite huge strides, Chittenden said there was still a lot to overcome.
“The megajoules of energy released in the experiment are really impressive in terms of fusion, but in practice this is equivalent to the energy needed to boil a kettle.”
“Much higher fusion energies can be achieved through ignition if we can figure out how to hold the fuel together longer, making more of it burn.”
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Construction of the National Ignition Facility (NIF) in the United States began in 1997 and was completed in 2009. The first experiments to test laser power began in October 2010.
Another function of the NIF is to monitor the status and security of the US nuclear weapons stockpile. Sometimes scientists who need to use the huge laser for fusion have to divide their time with experiments aimed at national security.
This is one of several projects around the world focused on fusion research. One of them is the ITER facility, budgeted in billions of euros and currently under construction in Cadarache, France.
ITER will take a different approach to laser powered fusion in the NIF; the facility in southern France will use magnetic fields to contain hot plasma—electrically charged gas. This concept is known as magnetic confinement fusion.
But building commercially viable fusion facilities capable of supplying grid power will require another giant leap.
“Transforming this concept into a renewable source of electrical energy is likely to be a long process and will involve overcoming substantial technical challenges, such as being able to recreate this experiment multiple times per second to produce a stable source of energy,” Chittenden points out.