A major milestone has been broken within the seek for fusion energy.
For the first time, a fusion reaction achieved a record energy efficiency of 1.3 megajoules output and, for the first time, exceeded the energy absorbed by fuel used to trigger it.
Although there is still a way to go, the result represents a significant improvement in previous yields: 8 times larger than the experiences made only a few months before & 25 times greater than the experiments carried out in 2018. This is a huge success.
The physicists of the national ignition facility at Lawrence Livermore National Laboratory will submitting a document for peer review.
“This result is a historical step for the fusion research of inertial confinement, which opens up a fundamentally new regime for the exploration and further advancement of our critical national security missions.
It is also a testament to innovation, ingenuity, commitment & grit of this team and many researchers in this area over the decades that steadfastly pursued this objective, “said Kim Budil, director of Lawrence Livermore laboratory.
“To me, this demonstrates one of the most important roles of national laboratories: our relentless commitment to tackle the greatest & most important scientific challenges and to find solutions where others might be dissuaded by obstacles.
Inertial confinement fusion involves the creation of something like a small star. Start with a fuel capsule, consist of deuterium & tritium – isotopes heavier than hydrogen. This fuel capsule is placed in a hollow gold chamber about size of a pencil eraser called a hohlraum.
Then, 192 high power laser rays are exploded at hohlraum, where they are converted to Xays. These x-rays implode the fuel capsule, heating & compressing it under conditions comparable to those of a star’s center – temperatures above 100 million degrees Celsius (180 million degrees Fahrenheit) & pressures above 100 billions of Earth’s atmospheres – turning the fuel capsule into a tiny blob of plasma.
And, just as hydrogen fuses into heavier elements at the core of a main sequence star, so does deuterium & tritium in fuel capsule. The whole process takes place in a few billionths of a second. The goal is to achieve ignition- a point where the energy generated by fusion process exceeds the total energy input.
The experiment, conducted on August 8, was just below this mark; the laser input was 1.9 megajoules. But it’s still extremely exciting, because according to the team’s measurements, the fuel capsule absorbed more than 5 times less energy than that generated during the fusion process.
This, the team said, is the result of pain-staking work refining experiment, including the design of hohlraum & capsule, improved laser precision, new diagnostic tools, & design changes to increase the capsule implosion speed, which transfers more energy to plasma hotspot where fusion occurs.
“Obtaining experimental access to thermonuclear combustion in the laboratory is the culmination of decades of scientific & technological work spanning nearly 50 years,” said Thomas Mason, director of the Los Alamos National Laboratory.
“This enables experiments that will test theory & simulation in the high energy density regime more rigorously than ever possible before & enable fundamental results in applied science & engineering.
The team plans to conduct follow-up experiments to see if they can replicate their outcome & study the process in more detail. The result also opens up new avenues for experimental research.
Physicists also hope to figure out how to further increase energy efficiency. Much of the energy is lost when laser light is converted into x-rays inside the hohlraum; large amount of proportion of the laser light instead goes in-to heat the walls of the hohlraum. Solving this problem will take us another important step towards fusion energy.
In the meantime, however, the researchers are extremely enthusiastic.
“Achieving ignition in a laboratory remains one of the great scientific challenges of this age and this result is an important step forward to achieving this objective,” said the physicist Johan Frenje of the MIT Plasma Science Center & Fusion Centre.
“It also allows the exploration of a fundamentally new and extremely difficult to access experimentally regime, furthering our understanding of fusion ignition & combustion processes, which is essential to validate & improve our simulation tools to support Stockpile stewardship.
“In addition, the result is historic as it represents the culmination of decades of hard work, innovation & ingenuity, large-scale team-work & relentless focus on the ultimate goal.
The team presented their results at the 63rd Annual Meeting of the APS Division of Plasma Physics.