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expert reaction to reports of advance in nuclear fusion from the Lawrence Livermore National Laboratory

There have been several reports that the federal Lawrence Livermore National Laboratory in California have carried out the first nuclear fusion experiment to achieve a net energy gain.


Dr Aneeqa Khan, Manchester-ISIS Neutron and Muon Source Research Fellow in Nuclear Fusion at The University of Manchester, said:

“Nuclear fusion is the process that powers the Sun, where two atoms fuse together, liberating huge amounts of energy. Recreating the conditions in the centre of the Sun on Earth is a huge challenge. We need to heat up isotopes of hydrogen (deuterium and tritium) gas so they become the fourth state of matter, called plasma. In order for the atoms to fuse together on Earth, we need temperatures ten times hotter than the Sun – around 100 million Celsius, and we need a high enough density of the atoms and for a long enough time. The reaction between the deuterium and tritium results in the production of helium and high energy (14 MeV) neutrons. Previously experimental fusion reactions have required the input of more energy into the plasma to fuse atoms together than has been output from the reaction itself. These results if true, are the first time in history that the fusion community have output more energy from the reaction than they put in. This is indeed a promising and exciting result, but we need to remember that this does not take into account the energy required to run the lasers that confine the reaction and other inefficiencies and losses.

“Fusion is considered a green source of energy as it does not release carbon dioxide into the atmosphere. If we can make it work it has the potential to provide a stable baseload of electricity to the grid, as well as potential for secondary applications such as hydrogen production or heating. It is not ready yet and therefore it can’t help us with the climate crisis now, however, if progress continues it has the potential to be part of a green energy mix in the latter half of the century and should be part of our long term strategy, while we use other existing technologies such as fission and renewables in the near term.

“This is a great scientific result, but we are still a way off commercial fusion. As mentioned above, we need an engineering net energy gain of the whole device that takes into account all plant inefficiencies. Building a fusion power plant also has many engineering and materials challenges. However, investment in fusion is growing and we are making real progress. We need to be training up a huge number of people with the skills to work in the field and I hope the technology will be used in the latter half of the century.

“Fusion is already too late to deal with the climate crisis, we are already facing the devastation from climate change on a global scale, looking at the floods in Pakistan, the droughts in China and Europe this summer alone. In the short term we need to use existing low carbon technologies such as fission and renewables, while investing in fusion for the long term, to be part of a diverse low carbon energy mix. We need to be throwing everything we have at the climate crisis. In all these technologies we need to be investing in training people from all over the world so that they can develop the solutions needed to face climate change. It is important to have both short and long term strategies.”


Prof Justin Wark, Professor of Physics at the University of Oxford and Director of the Oxford Centre for High Energy Density Science, said:

“This result is a major breakthrough in fusion science.  The Lawrence Livermore National Laboratory uses the largest laser in the world to compress heavy hydrogen to conditions similar to those in the centre of the sun. The lasers enter the ends of a centimetre-scale cylinder, hitting its inner walls, making them glow x-ray hot,  These x-rays then heat a sphere at the centre that contains the nuclear fuel.  The outside of the sphere vaporises and becomes a plasma, that rushes off the surface, creating an imploding ’spherical rocket’ which in a few billionths of a second reaches velocities of order 400 kilometres per second.  The subsequent ‘crunch’ at the centre is tailored in a specific way to make a hot spark in the middle, and the density of the compressed ‘fuel’ surrounding the spark  is so great that the nuclear fusion reaction takes place in about a tenth of a billionth of a second – faster than the tiny hot sphere can fly apart.  It is thus confined by its own inertia, and thus this method of fusion is called inertial confinement fusion.  The other major approach – magnetic fusion – uses the same heavy hydrogen fuel, but with a plasma far less dense than normal air, and thus the nuclei bump into each other less frequently, and in that approach the plasma needs to kept in its magnetic ‘bottle’ for several seconds in order for enough reactions to take place.  The aim of both methods is to get more energy out than is put in. 

“The Lawrence Livermore National Laboratory experiment shows that scientists can get more energy out than put in by the laser itself.  This is great progress indeed, but still more is needed: first we need to get much more out that is put in so to account for losses in generating the laser light etc (although the technology for creating efficient lasers has also leapt forward in recent years).  Secondly, the Lawrence Livermore National Laboratory could in principle produce this sort of result about once a day – a fusion power plant would need to do it ten times per second.  However, the important takeaway point is that the basic science is now clearly well understood, and this should spur further investment.  It is encouraging to see that the private sector is starting to wake up to the possibilities, although still long term, of these important emerging technologies.”


Dr Robbie Scott, of the Science and Technology Facilities Council’s (STFC) Central Laser Facility (CLF) Plasma Physics Group, who contributed to this research, said:     

“Fusion “ignition” occurs when the power emitted by the fusion reactions exceeds the losses. Experiments on the National Ignition Facility are a bit like striking a match, with this experiment the match kept burning. This is a momentous achievement after 50 years of research into Laser Fusion.             

“Fusion has the potential to provide a near-limitless, safe, clean, source of carbon-free baseload energy. This seminal result from the National Ignition Facility is the first laboratory demonstration of fusion ‘energy-gain’ – where more fusion energy is output than input by the laser beams. It cannot be understated what a huge breakthrough this is for laser fusion research. More importantly however, is that fact that it paves the way for the rapid development of Laser Inertial Fusion Energy – power generation by Laser Fusion.

“The experiment demonstrates unambiguously that the physics of Laser Fusion works. In order to transform NIF’s result into power production a lot of work remains, but this is a key step along the path. Next steps include the demonstration of even higher fusion energy-gain and the further development of more efficient methods to drive the implosion.

“This fantastic result was made possible by the work of hundreds of scientists and engineers over decades. My own contribution was to discover that if NIF’s implosions were not spherical, this would reduce the efficiency of the implosion and so the number of fusion reactions. Importantly, I also showed that certain non-spherical implosion shapes would appear to be perfectly spherical using NIF’s X-ray imaging diagnostics. This led to the development of new diagnostics for NIF which confirmed the implosions were non-spherical, just as predicted. This resulted in a multiyear effort at NIF to make the implosions as spherical as possible, improving NIF’s fusion yield.”


Prof John Collier, Director of the UK’s Central Laser Facility [CLF], said:

“The CLF’s Vulcan laser has been a workhorse for laser fusion research for decades, with teams from both UK universities and internationally, performing pioneering research advancing our understanding of the plasma physics underpinning Laser Fusion. The CLF are also leaders in the development of high efficiency lasers which will be required to generate power via Laser Fusion in the future.

“We welcome this milestone result from NIF which is fantastic news. It is great that the CLF and UK academic community have been part of this journey. We now look forward to translating this result into what has real potential to be a long-term green energy solution.”


Will Davis, a member of the IET’s nuclear steering group, said:

“This is certainly a fantastic development. NIF have clearly taken the learning from their achievement last year and used it to significantly improve the effectiveness and efficiency of their experiment. As the researchers say, they are still verifying their results, however, if the preliminary information is accurate this shows that NIF has achieved another milestone, to generate more energy than is needed to run the experiment itself. This recent achievement shows that inertial confinement fusion can achieve net energy gain, which demonstrates the technical feasibility of fusion power and validates this approach to providing clean energy.”


Tony Roulstone, lecturer in nuclear energy at the University of Cambridge, said:

“It is reported that the National Ignition Facility (NIF) has surpassed one of its own targets to exceed scientific energy gain.  They put 1.8 MJ and got 2.5 MJ out – proving that energy can been successfully released and gained by a Deuterium-Tritium fusion reaction. This is positive – the failure to achieve scientific energy gain in 2012 ended the run of experiments for which NIF was built. Now they have worked on the design and the make-up of the target and the shape of the energy pulse to get much better results.

“Although positive news, this result is still a long way from the actual energy gain required for the production of electricity.  That’s because they had to use 500 MJ of energy into the lasers to deliver 1.8 MJ to the target – so even though they got 2.5 MJ out, it’s still far less than the energy they needed for the lasers in the first place.  In other words, the energy output (largely heat energy) was still only 0.5% of the input.  An engineering target for fusion would be to recover much of the energy used in the process and get an energy gain of double the energy that went into the lasers – it needs to be double because the heat must be converted to electricity and you lose energy that way.

“Therefore we can say that this result from NIF is a success of the science – but still a long way from providing useful, abundant, clean energy.”


Prof Jeremy Chittenden, Professor of Plasma Physics at Imperial College London, said:

“Everyone working on fusion has been trying to demonstrate for over 70 years that it’s possible to generate more energy from fusion than you put in. If what has been reported is true and more energy has been released than was used to produce the plasma, that is a true breakthrough moment which is tremendously exciting. It proves that the long sought-after goal, the ‘holy grail’ of fusion, can indeed be achieved.

“To turn fusion into a power source we’ll need to boost the energy gain still further. We’ll also need to find a way to reproduce the same effect much more frequently and much more cheaply before we can realistically turn this into a power plant.”


Dr Brian Applebe, a Research Associate in the Department of Physics at Imperial College London, said:

“Demonstrating energy gain in a fusion experiment would be a highly significant scientific and technological achievement. Firstly, it would show that we can create and control a source of fusion energy in the laboratory. This has been one of the biggest obstacles to developing fusion energy for decades. Secondly, it would allow scientists to study in detail what is happening in the ‘burning plasma’ in which the fusion reactions are occurring. This would help scientists to optimize the amount of energy that could be obtained from fusion experiments.”


Prof Gianluca Gregori, Professor of Physics at the University of Oxford who specialises in high power lasers and fusion energy, said:

“For many years fusion energy has been described as the holy grail of the world’s energy problems – a limitless and clean energy source that would address the ever-increasing demands free from carbon emissions. The scientists at the Lawrence Livermore National Laboratory have achieved the long-sought milestone of proving for the first time breakeven thermonuclear fusion in the laboratory. The amount of energy released in the fusion reactions exceeded that of the input laser energy, demonstrating a positive energy gain. The fusion approach used at Lawrence Livermore requires the thousand-fold compression of matter to ultra-high densities and temperatures to mimic the compressional effect of gravity in the sun, nature’s very effective nuclear fusion reactor. While this is not yet an economically viable power plant (the costs of targets are still exorbitant, and the amount of energy released is yet smaller than wall plug electricity costs), the path for the future is much clearer.’

“Today’s success rests upon the work done by many scientists in the US, UK and around the world. With ignition now achieved, not only fusion energy is unlocked, but also a door is opening to new science. Applications of inertial fusion-related research include the ability to study processes related to astrophysical turbulence and magnetic field generation in galaxy clusters, and to unravel the dynamics of matter compressed under extreme pressures as found in the cores of giant planets.”


Dr Mark Wenman, Reader in Nuclear Materials at Imperial College London, said:

“So far despite 70 years of research no one has got more energy out of a fusion reaction than they have needed to put in. The record was around 70% (i.e. a net loss of energy). 

“This new announcement by Lawrence Livermore, if proven to be true, therefore sets a remarkable point in human history, which in future could usher in an era of green, secure and essentially inexhaustible form of compact energy, without long-lived nuclear waste.  Of course this announcement is likely to be of more scientific significance than a practical one, but as a proof of concept should help more funding flow into nuclear fusion research bringing the time when we can connect a fusion plant to the grid that bit closer.”


Prof Robin Grimes FRS FREng, professor of materials physics, Imperial College London, said:

“This is a key step on a possible pathway to commercial fusion. It demonstrates and underpins our basic understanding of the physics and is an engineering triumph. Nevertheless, extracting this energy in away that it can be harnessed and developing the materials that can stand up to continuous operation are massive challenges. There is no doubt, the prize is worth the effort. Success, however long it takes, would be transformational.”


Quotes from the Spanish SMC:



Declared interests

Prof Grimes: “none to declare.”

Dr Wenman: “none.”

Prof Chittenden and Dr Applebe contribute to the work of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory.

Prof Wark is the UK academic member of the National Ignition Facility Peer Review Panel that gives advice on the fusion program at Lawrence Livermore National Laboratory.

For all other experts, no reply to our request for DOIs was received.

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