With the help of 192 lasers, scientists have made a breakthrough in nuclear fusion.

Researchers working on fusion energy at the Lawrence Livermore National Laboratory in California revealed on Tuesday that they have achieved a long-awaited breakthrough in simulating the sun's power in a lab.
This prompted enthusiasm among the general people since fusion, the nuclear reaction that creates stars, has long been discussed by scientists as a potential future source of abundant energy.
The outcome that was revealed on Tuesday is the first fusion reaction that took place in a lab environment and really created more energy than it consumed to initiate the reaction.
If fusion can be implemented on a large scale, it will provide a source of energy that is free of the harmful long-lived radioactive waste produced by today's nuclear power plants, which use the splitting of uranium to produce energy, as well as the pollution and greenhouse gases brought on by the burning of fossil fuels.
The planets' atmospheres are heated and illuminated by sunlight produced by the continuous fusion of hydrogen atoms into helium within the sun and stars. Fusion proves to be a very clean energy source in Earth's experimental reactors and laser laboratories.
However, there was always a nagging qualification. Scientists' experiments used up more energy than the fusion reactions produced in all of their attempts to regulate the chaotic power of fusion.
This changed on December 5 at 1:03 in the morning when 192 massive lasers at the laboratory's National Ignition Facility blasted a tiny cylinder the size of a pencil eraser that contained a frozen nubbin of hydrogen coated in diamond.
The cylinder was vaporized by the laser beams that entered it from the top and bottom. The heavier types of hydrogen, deuterium and tritium, were compressed into a fuel pellet the size of a BB as a result of the internal onslaught of X-rays that were produced.
The hydrogen pellet was bombarded with 2.05 megajoules of energy, or about a pound of TNT, in a brief period of time that lasted less than 100 trillionths of a second. A flood of neutron particles, a byproduct of fusion, came out, each carrying around 3 megajoules of energy, an increase in energy of 1.5.
This went above what laser fusion specialists refer to as the ignition threshold, or the point at which the energy produced by fusion equals the energy of the incoming lasers that initiate the reaction.
The National Ignition Facility's development began in 1997, and the successful experiment eventually achieves the ignition aim that was pledged at that time. However, when operations started in 2009, the facility barely produced any fusion energy, which was an embarrassing letdown given the federal government's $3.5 billion investment.
Scientists from Livermore finally reported some progress in 2014, but the amount of energy generated was negligible — only enough to power a 60-watt light bulb for five minutes. Over the following few years, there was very little advancement.
The facility then produced a far larger energy burst in August of last year, equal to 70% of the energy from the laser light.

The program director for weapons physics and design at Livermore, Mark Herrmann, stated in an interview that the researchers then carried out a series of experiments to better understand the unexpected success in August and that they worked to increase laser energy by almost 10% and improve the design of the hydrogen targets.
In September, the first laser shot at 2.05 megajoules was made, and that first attempt generated 1.2 megajoules of fusion energy. The spherical hydrogen pellet was not crushed equally, and some of it practically squirted out the side and did not reach fusion temperatures, according to analyses.
The researchers made certain modifications that they thought would improve the results.
According to Dr. Herrmann, "the forecast before the shot was that it may go up by a factor of two." Actually, it increased a little bit more than that.
The National Ignition Facility's primary objective is to carry out experiments that will aid in the maintenance of American nuclear weapons. The implications for generating energy right away are therefore uncertain.
Fusion would effectively be an emissions-free source of energy, reducing the need for coal and gas-burning power plants that annually release billions of tons of climate-warming carbon dioxide into the atmosphere.
But if ever, it will be a while before fusion is accessible on a broad, practical basis.
According to the majority of climate scientists and decision-makers, the world must achieve net-zero emissions by 2050 in order to limit warming to 2 degrees Celsius or the even more ambitious aim of 1.5 degrees Celsius.

Tokamaks are doughnut-shaped reactors that have been the mainstay of fusion research up to now. A plasma is a cloud of positively charged nuclei and negatively charged electrons created when hydrogen gas is heated to temperatures high enough to remove the electrons from the hydrogen nuclei. As the nuclei fuse together, energy is released as neutrons that shoot outward are trapped by magnetic fields inside the doughnut-shaped plasma.
Although the work at NIF uses a different methodology, not much has been done to make the concept of a laser fusion power plant a reality up to this point. Technology and science both face very big obstacles, according to Dr. Budil.
Although NIF is the most potent laser in the world, it is also the slowest and least effective since it uses technology that is many decades old.
The device, which is roughly the size of a sports stadium, is made to conduct simple scientific experiments rather than serve as a model for the production of power.

Ten shots every week on average. A commercial laser fusion plant would require substantially faster lasers, maybe 10 times faster, capable of firing at a machine gun pace.
Additionally, NIF still uses a lot more energy than the fusion reactions do.
Even though the most recent experiment yielded a net energy gain in comparison to the energy of the 2.05 megajoules in the entering laser beams, NIF still needed to draw 300 megajoules from the electrical grid in order to produce the brief laser pulse.

Even while other kinds of lasers are more effective, researchers say a practical laser fusion power plant will likely need far bigger energy increases than the 1.5 seen in this most recent fusion pulse.
Different iterations of the NIF experiment are being studied by researchers elsewhere. The hydrogen might be heated more effectively using other kinds of lasers with different wavelengths.

Some scientists prefer a "direct drive" strategy for laser fusion, in which the laser light heats the hydrogen directly. The hydrogen would absorb more energy as a result, but this could potentially lead to unstable fusion processes.
The scientists working on the nuclear stockpile, which is the NIF's main objective, will benefit from the findings that were announced on Tuesday. Scientists are trying to replace the data they used to get from underground nuclear bomb detonations, which the United States ceased in 1992, by conducting these nuclear reactions in a lab at a less damaging scale.

Dr. Herrmann stated that the facility's increased fusion output will generate more data "that allows us to preserve the confidence in our nuclear deterrent without the necessity for further underground testing." The output, which is 30,000 trillion watts of power, "creates very harsh situations in itself" that are more akin to nuclear weapons exploding.

The purpose of this particular Livermore experiment, according to Riccardo Betti, chief scientist of the Laboratory for Laser Energetics at the University of Rochester, who was not participating, is to show that a thermonuclear fuel may be ignited for the first time in a laboratory setting.
And this was completed, he continued. "So this is a fantastic outcome."

CC : Kenneth Chang , NY times