February 5, 2023

Scientists at a federal nuclear weapons facility have made potentially significant advances in fusion research, which could produce abundant energy in the future, an administration official said.

The Energy Department is expected to announce the development on Tuesday, calling it a “significant scientific breakthrough” at California’s Lawrence Livermore National Laboratory. Energy Secretary Jennifer Granholm, the White House and other DOE officials are expected to attend.This The Financial Times reported on Sunday The scientific advance involves the National Ignition Facility, or NIF, which uses giant lasers to create conditions that briefly simulate the detonation of a nuclear weapon.

The administration official, who spoke on condition of anonymity to discuss the unpublished results, said NIF’s fusion experiments achieved what’s known as ignition, in which fusion energy is equal to the laser energy that kicked off the reaction. Ignition is also known as a power gain.

Such a development would improve the United States’ ability to sustain its nuclear weapons without nuclear testing and could lay the groundwork for future advances that could one day lead to the use of laser fusion as an energy source.

While it has not been announced publicly, the news is spreading rapidly among physicists and other scientists who study fusion.

“A scientist friend sent me a note yesterday that Livermore just surpassed an energy gain last week and will announce the results on Tuesday,” said Stephen Bo, a retired plasma physicist who has long been critical of the NIF. Dana said in a report. Email Monday morning. “They deserve credit for achieving their goals.”

Fusion is the thermonuclear reaction that powers the sun and other stars — the fusing of hydrogen atoms into helium. Helium is slightly less massive than the original hydrogen atom. Thus, the difference in mass translates into a burst of energy according to Einstein’s iconic E=mc² equation.

Fusion, which could be produced in a controlled manner here on Earth, could mean a source of energy that wouldn’t produce greenhouse gases like coal and oil, or dangerous long-lived radioactive waste, like current nuclear power plants.

Most fusion work to date has employed circular reactors known as tokamaks. Inside the reactor, hydrogen gas is heated to a temperature high enough that electrons are stripped from the hydrogen nuclei to form what’s known as a plasma — a cloud of positively charged nuclei and negatively charged electrons. The magnetic field traps the plasma in a donut shape, and the nuclei fuse together, releasing energy in the form of neutrons that fly outward.

However, Tuesday’s announcement involved a different approach. The NIF consists of 192 giant lasers that fire simultaneously at a metal cylinder the size of a pencil eraser. The cylinder is heated to about 5.4 million degrees Fahrenheit, vaporizes, and produces an X-ray implosion that heats and compresses BB-sized particles of frozen deuterium and tritium, two heavier forms of hydrogen. The implosion fuses hydrogen into helium, creating fusion.

The main purpose of the NIF, which cost $3.5 billion to build, is to conduct experiments and help the United States maintain its nuclear weapons without conducting nuclear test explosions. Backers also say it could advance fusion research that could lead to viable commercial power plants.

However, NIF hardly produces any fusion initially. In 2014, the Livermore scientists finally reported success, but at the time they were generating tiny amounts of energy—about as much energy as a 60-watt light bulb consumes in five minutes.

Last year, Livermore scientists reported a major leap forward, a burst of energy — 10 petawatts of power — equivalent to 70 percent of the energy of a laser hitting a hydrogen target.

But the explosion — essentially a tiny hydrogen bomb — lasted only 100 trillionths of a second.

A report in the Financial Times on Sunday suggested that Livermore would announce that in the latest experiment, fusion produced more energy than lasers capable of hitting hydrogen targets.

For this to happen, the fusion reaction has to be self-sustaining, which means that the mass of particles flowing out from the hot spot in the center of the sphere heats the surrounding hydrogen atoms and causes them to fuse as well.

An important caveat is that the statement focuses on laser energy hitting hydrogen targets. The NIF’s lasers are extremely inefficient, meaning that only a fraction of the energy used to power the lasers actually makes it into the beam itself.

More modern technologies, such as solid-state lasers, are more efficient, but are still far from 100% fusion; for this to be practical, the fusion energy output must be at least several times that of the incident laser light.

Do not.

Even if scientists figure out how to generate larger fusion bursts, huge engineering hurdles will remain.

NIF’s experiments study bursts one burst at a time.

A practical fusion power plant using this concept would require a machine gun pace of laser pulses, with new hydrogen targets sliding into place with each pulse. Then, the large number of neutrons flying out of the fusion reaction must be converted into electricity.

The laser complex occupies an area the size of three football fields — too big, too expensive and too inefficient for a commercial power plant.

A fabrication process must be developed to mass-produce precise hydrogen targets.



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