In August, physicists at Lawrence Livermore National Laboratory's (LLNL) National Ignition Facility (NIF) discovered that they may have finally crossed the barrier of "ignition" of inertial confinement fusion. They have now verified it. They experimented with extracting more energy from the fusion reactor than was originally required to fuse the material.
The event released 1.3 Megajoules of fusion energy – an eight-fold improvement on the test conducted this past spring, and 25 times better than the record-breaking experiments in 2018. The findings are published in the journal Nature.
“In these experiments we achieved, for the first time in any fusion research facility, a burning plasma state where more fusion energy is emitted from the fuel than was required to initiate the fusion reactions, or the amount of work done on the fuel,” co-lead author Annie Kritcher said in a statement.
The fusion approach at the NIF is known as Inertial Confinement Fusion. This is different from what is being investigated in fusion reactors such as Tokamak and Stellarators. There the energy is extracted by continuous flow from the hot fusing plasma. In Inertial confinement fusion, energy is instead extracted from discrete events. Using the world’s most energetic laser, small pellets of fuel are ignited by heating and compressing, creating fusion and releasing a huge amount of energy that can be turned into electricity.
The whole facility is the size of three football fields but the laser target, once heated, creates a hot spot the diameter of a human hair. In that confined space, the fusing pellet releases 10 quadrillion watts of fusion power for 100 trillionths of a second.
The breakthrough was possible thanks to a much deeper understanding of what is actually happening in that confined space. Models were tweaked and tested, the length of laser pulses was played with, as well as the design of the hohlraum – the enclosing radiation cavity around the pellet.
“There is much work yet to be done and this is a very exciting time for fusion research,” Kritcher said. “Following this work, the team further improved hohlraum efficiency in both platforms, increasing hot spot pressure which resulted in higher performance and the record 1.35 MJ HYBRID-E experiment.”
Even though it's a fantastic milestone, the team considers this fusion achievement a “basecamp.” From here, they plan to improve and build on the current approach, with the goal to reach even higher pressures and thus even higher energy released from this type of fusion.
Reference(s): Nature
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