Article By : Maurizio Di Paolo Emilio
Scientists at the NIF have achieved fusion ignition.
Scientists at the world’s largest nuclear fusion facility have achieved the phenomenon known as ignition, or the creation of a nuclear reaction that generates more energy than it consumes.
The results of the discovery at the U.S. National Ignition Facility (NIF) of the Lawrence Livermore National Laboratory (LLNL) in California, conducted on Dec. 5, were announced a few days ago by the administration of U.S. President Joe Biden. That research aims to harness nuclear fusion—the phenomenon that powers the sun—to provide an almost unlimited source of clean energy on Earth.
The nuclear fusion process produced approximately 1.5× the amount of energy introduced into the reactor. This is a technical advancement that unquestionably closes the gap for the realization of a clean and possibly endless source of energy, such as that which occurs in the stars.
But it will still take many years of study and development and, most crucially, financing. By unlocking the ignition at the NIF, it will be possible to investigate the severe circumstances at the heart of nuclear explosions and answer long-standing concerns regarding energy supply safety and management.
The NIF cost $3.5 billion and produced 1.37 megajoules (MJ) of fusion energy last year. This represents about 70% of the energy in lasers, making this facility the closest in the world to produce net energy gain.
“This is a landmark achievement for the researchers and staff at the National Ignition Facility who have dedicated their careers to seeing fusion ignition become a reality, and this milestone will undoubtedly spark even more discovery,” said U.S. Secretary of Energy Jennifer M. Granholm during the conference.
“We have had a theoretical understanding of fusion for over a century, but the journey from knowing to doing can be long and arduous,” said Arati Prabhakar, the president’s Chief Advisor for Science and Technology and Director of the White House Office of Science and Technology Policy. “Today’s milestone shows what we can do with perseverance.”
“Monday, December 5, 2022, was an important day in science,” said National Nuclear Security Administration (NNSA) Administrator Jill Hruby. “Reaching ignition and a controlled fusion experiment is an achievement that has come after more than 60 years of global research, development, engineering and experimentation.
“Last week, our improved predictions through machine learning and the amount of data collected indicated that we had a more than 50% chance of exceeding the goal set 160 years ago, when it was proposed that lasers could be used to produce fusion ignition in the laboratory,” said Kim Goodell, director of LLNL. “At the time, it was a very bold idea, and the laser had just been invented. It was far from the mature tool we know today. But that’s what national laboratories are for: tackling the most difficult scientific issues, learning from inevitable failures and developing the next great idea.”
U.S. Secretary of Energy Jennifer M. Granholm and Under Secretary for Nuclear Security and National Nuclear Security Administration Administrator Jill Hruby announce a major scientific breakthrough accomplished by researchers at DoE’s Lawrence Livermore National Laboratory. Joining the Secretary and Under Secretary is White House Office of Science and Technology Policy Director Arati Prabhakar, NNSA Deputy Administrator for Defense Programs Marvin “Marv” Adams and LLNL Director Kim Budil. (Source: YouTube)
Fusion technology
Nuclear fusion is a significant natural phenomenon, as it is essential for the functioning of stars like the sun. As is already the case with fission reactors, the potential of conducting “controlled” nuclear fusion processes to generate power on an industrial scale has been investigated since the post-war era.
In the past year, nuclear fusion has become increasingly feasible. Venture capitalists invest billions in firms racing to construct a fusion power plant within the next decade or more. Through the Inflation Reduction Act and the Department of Energy, the Biden administration is introducing tax credits and grant programs to assist businesses in determining how to implement this form of energy.
Before nuclear fusion becomes a realistic technology, at least 20 years will pass as an experimental technology. Researchers at the National Ignition Facility at Lawrence Livermore National Laboratory in California have claimed a significant success in nuclear fusion research. For a power plant to be commercially viable, it must provide enough energy to power lasers and accomplish continuous ignition. To have commercial fusion energy, it is necessary to create a large number of fusion ignitions each minute.
Nuclear physicists warn, however, that obstacles persist. The energy system would need to be reconfigured, and the cost of fusion energy supply would need to decrease. We are unquestionably at a very exciting moment, but we must recognize that it will take time to tackle the severe problems in physics.
Climate change’s effects are increasing, and time is running out. Consequently, fusion energy may be necessary. Companies will need to develop methods for deploying the technology on a massive scale. The most crucial factor is cost-effectiveness. At the same time, investments must incorporate renewable energy. Additionally, institutions must produce scientists capable of working on fusion technology. Companies that produce fusion energy must invent technologies that produce more energy than they use.
Inspecting the final optics at NIF (Source: Lawrence Livermore National Laboratory)
Clean energy derived from nuclear fusion
The goal of nuclear fusion is a clean and perhaps limitless energy source. It differs greatly from nuclear fission, which generates energy by utilizing the phenomenon of atom splitting. This is the basis for fission power plants, which have existed for a long time and have been the subject of intense discussion because of the potential dangers posed by atom splitting, such as radioactive by-products, in addition to producing energy.
The process of nuclear fusion is profoundly distinct: To replicate the process that occurs in stars, two hydrogen-like atoms must be brought closer together until they fuse.
For fusion to occur, it is necessary to bring the two nuclei very close together to overcome their electrostatic repulsion. To achieve this, magnetic fields must be used to confine the nuclei to a very high density and temperature, which is a technically challenging and energy-intensive process.
Most scientists’ efforts are devoted to the construction and operation of facilities capable of isolating these extremely high temperatures. This is because the atoms within the reactors are more rarefied than they are in stars, and the heat helps to accelerate them to facilitate the fusion process.
This material is referred to as plasma. The extreme temperatures of this matter mean it must be contained; otherwise, the surrounding structure would melt. Superconducting magnets, capable of creating magnetic fields hundreds of thousands of times stronger than those on Earth, keep the plasma elevated and contained within the huge ring in which it circulates.
Technician Joseph Florio prepares a tritium-hydrogen-deuterium (THD) target for an experiment. THD targets are a variant of deuterium-tritium ignition targets that have been “dudded” by mixing the fusion fuel with hydrogen (Source: Lawrence Livermore National Laboratory)
NIF’s achievement
A tiny gold cylinder holding a frozen ball of hydrogen, deuterium and tritium isotopes was bombarded with about 2 MJ of energy by 192 lasers at the NIF facility. The energy surge caused the capsule to collapse, producing temperatures only seen in stars. The hydrogen isotopes fused into helium, releasing further energy and triggering a cascade of fusion processes. About 3.15 MJ of energy was released, which is approximately 54% more energy than what originally entered the reaction and more than double the previous record of 1.3 MJ, according to laboratory analysis.
The experiment qualifies as ignition, a standard metric for fusion reactions that compares the amount of energy introduced into the target with the amount of energy released.
However, the consumption of the 192 lasers during the procedure must be taken into account.
About 300 MJ were taken from the grid to power the laser, which was not meant to be energy-efficient. Rather, the laser was meant to provide as much energy as possible to make these extraordinary circumstances conceivable in the laboratory. In order to accomplish inertial fusion as a source of energy, it is necessary to carry out a number of operations and to utilize sophisticated equipment.
To contain the plasma, the fusion process requires a specific containment system known as “laser confinement,” in which several hundred lasers reproduce an effect similar to that generated by gravity. This process simulates the conditions that initiate the nuclear fusion reaction that occurs in stars, including the sun. For reference, the European ITER project is based on “magnetic confinement”.
More work required
Scientists recognize that major advances have been made and that NIF was not intended as a commercial solution.
To accomplish ignition, NIF scientists made many modifications prior to the most recent laser blast, based in part on analysis and computer modelling of last year’s trials. In addition to raising laser power by about 8%, the scientists constructed a new target with fewer flaws and modified the method by which laser energy was transferred to the target to achieve a more spherical implosion.
According to NIF specialists, the most powerful laser in the world is used in this experiment to create X-rays that collapse a tiny capsule and form a highly heated, high-pressure plasma. Plasma’s tendency is to lose energy instantly; it wants to erupt and radiate, and it seeks a mechanism to cool itself.
However, fusion processes add heat to the plasma, causing it to heat up. Therefore, there is a competition between heating and cooling. Moreover, when the plasma’s temperature rises, the fusion reaction rate increases, resulting in more fusion, which in turn causes further heating. For several decades, scientists have accomplished more cooling processes compared to heating processes.
On Dec. 5, however, the fusion plasma was heated to extremely high temperatures, resulting in a yield of 3.15 MJ.
According to the NIF team, it is the responsibility of all scientists to specify the experiment’s input conditions to obtain the necessary plasma conditions. This covers the target’s shape, size, composition and more, in addition to the laser pulse. The NIF team explained that we do not simultaneously strike the target with all of the laser’s energy.
“In order to accomplish the necessary circumstances, we establish certain powers at specified times, and we achieve this using a variety of methods, including simulations of sophisticated plasma physics, analytical models and comparisons with experimental data,” the NIF team said during a roundtable presentation of the results.
The ultimate objective is to develop a design capable of achieving the severe conditions necessary for fusion ignition in NIF. This allows scientists to obtain temperatures of about 150 million degrees Celsius and pressures more than twice as high as the center of the sun. To reach these circumstances, attempts have been undertaken to employ more powerful lasers and to increase the thickness of the capsule carrying the fusion fuel.
The fuel capsule is a BB-sized diamond shell that must be as flawless as possible. Over the past 16 years, efforts have been made to consistently increase the quality of these shells to their current condition, according to experts. This project is a continuation of decades of capsule development work conducted at Livermore and elsewhere.
Today’s shells are nearly perfectly spherical, 100× smoother than a mirror and linked to a tiny tube. Through this tube with a diameter approximately 50× larger than a hair, fuel is delivered into the shell. Achieving perfection is extremely tough, according to experts. So, we are not quite there; today’s shells still have minor flaws. These faults have the capacity to influence the experiment despite their minor size.
To demonstrate that the form of fusion explored at NIF is a feasible means of producing energy, the yield efficiency (the ratio of the energy released to the energy consumed to create the laser pulses) must grow by several orders of magnitude.
Researchers will also need to significantly improve the rate at which lasers create pulses and clean the target chamber to prepare it for re-burning.
In the near future, researchers at LLNL will refine the analyses received from this experiment and attempt further research on nuclear fusion energy to realize a potentially limitless, fossil-fuel–free source of clean energy.
This article was originally published on EE Times.
Maurizio Di Paolo Emilio has a Ph.D. in Physics and is a Telecommunications Engineer. He has worked on various international projects in the field of gravitational waves research designing a thermal compensation system, x-ray microbeams, and space technologies for communications and motor control. Since 2007, he has collaborated with several Italian and English blogs and magazines as a technical writer, specializing in electronics and technology. From 2015 to 2018, he was the editor-in-chief of Firmware and Elettronica Open Source. Maurizio enjoys writing and telling stories about Power Electronics, Wide Bandgap Semiconductors, Automotive, IoT, Digital, Energy, and Quantum. Maurizio is currently editor-in-chief of Power Electronics News and EEWeb, and European Correspondent of EE Times. He is the host of PowerUP, a podcast about power electronics. He has contributed to a number of technical and scientific articles as well as a couple of Springer books on energy harvesting and data acquisition and control systems.
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