- Paul Rincon Bar
- Science Editor, BBC News website
An American scientific institute is on the cusp of a long-term goal in nuclear fusion research.
The National Ignition Facility uses a powerful laser to heat and compress hydrogen, resulting in fusion.
One experiment suggests that the goal of ‘ignition’, where the energy released by fusion exceeds the energy provided by the laser, is now within reach.
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Harnessing fusion, the process that powers the sun, could provide a clean and unlimited source of energy.
In a process called inertial confinement fusion, 192 laser beams from NIF – the world’s most powerful laser – are directed at a pepper-sized capsule containing deuterium and tritium, different forms of the element hydrogen.
The fuel is then compressed to a density 100 times greater than that of lead and heated to 100 million degrees Celsius, a temperature higher than that of the center of the Sun.
These conditions make it possible to launch thermonuclear fusion.
An experiment conducted on August 8 obtained 1.35 megajoules of energy, or about 70% of the laser energy supplied to the fuel capsule.
Achieving ignition means obtaining a fusion efficiency greater than the 1.9 MJ that the laser provides.
“This is a huge step forward for fusion and for the entire fusion community,” Debbie Callahan, a physicist at Lawrence Livermore National Laboratory, which hosts the NIF, told BBC News.
To gauge progress, the yield for this month’s trial is eight times higher than the previous NIF record, set in the spring of 2021, and 25 times the yield for trials conducted in 2018.
Professor Jeremy Chittenden, co-director of the Center for Inertial Fusion Studies at Imperial College London.
FNI scientists also believe they’ve achieved what’s called a “hot plasma,” meaning that the fusion reactions themselves provide the heat needed for further fusion.
This phenomenon is necessary for the process to be self-sufficient.
“Spontaneous combustion is essential for high efficiency,” says Dr. Callahan.
“The combustion wave must propagate through the fuel at a high intensity in order to obtain a large amount of fusion energy.”
“We believe this trial falls under this system, although we are still running analyzes and simulations to make sure we understand the outcome.”
The next step, according to Dr. Callahan, will be to repeat the experiments.
“This is a fundamental aspect of experimental science. We need to understand how reproducible the results are and how sensitive small changes are,” she says.
“Next, we have some ideas for improving this design and we’ll start working on it next year.”
Professor Chittenden explains: “The amount of megajoule energy released during the experiment is really impressive in terms of fusion, but in practice this is equivalent to the energy required to boil a kettle.”
He adds, “Much higher fusion energies could be achieved by ignition if we could keep the fuels together for longer, in order to burn more of it. That would be the next horizon for self-confinement fusion.”
Today’s nuclear energy relies on a process called fission, in which a heavy chemical element splits to produce lighter elements.
Fusion works by combining two lighter elements to make a heavier element.
Construction of the National Ignition Facility began in 1997 and was completed in 2009. The first trials to test the power of the laser began in October 2010.
Another function of the National Islamic Fund is to help ensure the security and reliability of the United States’ stockpile of nuclear weapons.
Sometimes scientists who want to use massive lasers for fusion see their time cut short by experiments focused on national security.
But in 2013, the BBC reported that in experiments at the NIF, the amount of energy released by fusion exceeded the amount of energy absorbed by the fuel – a breakthrough and the first of its kind for any fusion facility in the world.
The results of these tests were then published in the journal Nature.
The NIF is one of many projects around the world that aim to advance fusion research.
Among these facilities is the multi-billion-euro Iter facility currently being built in Cadarache, France.
Iter will take a different approach to laser fusion for NIF.
The facility in southern France will use magnetic fields to contain hot, electrically charged plasma gas.
This concept is known as magnetic containment fusion (MCF).
But building commercially viable fusion facilities capable of powering the grid will require another giant leap.
“Converting this concept to a renewable electrical energy source is likely to be a lengthy process and will require overcoming significant technical challenges, such as being able to recreate this experiment multiple times per second to produce a stable source of energy.” , says Professor Chittenden.
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