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Finally, a Fusion Reaction Has Generated More Energy Than Absorbed by the Fuel

posted by FatPhil on Thursday December 16 2021, @01:37AM   
from the high-precision dept.

upstart writes:

Finally, a Fusion Reaction Has Generated More Energy Than Absorbed by The Fuel:

A major milestone has been breached in the quest for fusion energy.

For the first time, a fusion reaction has achieved a record 1.3 megajoule energy output – and for the first time, exceeding energy absorbed by the fuel used to trigger it.

Although there's still some way to go, the result represents a significant improvement on previous yields: eight times greater than experiments conducted just a few months prior, and 25 times greater than experiments conducted in 2018. It's a huge achievement.

[...] Inertial confinement fusion involves creating something like a tiny star. It starts with a capsule of fuel, consisting of deuterium and tritium – heavier isotopes of hydrogen. This fuel capsule is placed in a hollow gold chamber about the size of a pencil eraser called a hohlraum.

Then, 192 high-powered laser beams are blasted at the hohlraum, where they are converted into X-rays. These X-rays implode the fuel capsule, heating and compressing it to conditions comparable to those in the center of a star – temperatures in excess of 100 million degrees Celsius (180 million Fahrenheit) and pressures greater than 100 billion Earth atmospheres – turning the fuel capsule into a tiny blob of plasma.

And, just as hydrogen fuses into heavier elements in the heart of a main-sequence star, so too does the deuterium and tritium in the fuel capsule. The whole process takes place in just a few billionths of a second. The goal is to achieve ignition – a point at which the energy generated by the fusion process exceeds the total energy input.

The experiment, conducted on 8 August, fell just short of that mark; the input from the lasers was 1.9 megajoules. But it's still tremendously exciting, because according to the team's measurements, the fuel capsule absorbed over five times less energy than it generated in the fusion process.[...]

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Your humble editor often gets a little snarky about the presentation of fusion energy results, possibly due to sloppy journalism or press releases, possibly due to scientists who don't want the magnitude of the shortfalls to be obvious, but finally it seems all the figures are non-misleading, and finally it seems they're actually getting close. Time for tokamaks to up their game - the race is on!

Original Submission

• Re:Net negative (Score: 5, Informative) by Anonymous Coward on Thursday December 16 2021, @04:27AM

  by Anonymous Coward on Thursday December 16 2021, @04:27AM (#1205498)

  The article title is poorly worded. The abstract of the talk that this story derived from is actually pretty descriptive and better than the science alert overview:

  One of the scientific milestones in fusion research on the path to ignition is creating a burning plasma. A burning plasma occurs when the energy deposited by the fusion-produced alpha particles is the dominant source of heating of the plasma – this is a necessary step to reach ignition. Recent experiments on NIF have reached this state using two indirect-drive designs; both designs use larger capsules than had been used previously while maintaining other important parameters of implosion velocity, low-mode symmetry, late-time ablation pressure, and high Z mix. To drive larger capsules with the same amount of laser energy, these capsules had to be driven in a similar size hohlraum; making maintaining a symmetric drive more difficult, and requiring the use of additional techniques to mitigate low-mode asymmetry.

  Progress toward ignition has been made in steps. At each step, a combination of experimental data (including improved diagnostics), theory, and modeling is used to identify and understand the limiters in performance. New designs are developed using this understanding and generally results in an increase in performance until the next limiter dominates. This cycle has produced several physics milestones on the way to ignition. First was fuel gain, where the neutron yield exceeds the energy in the deuterium-tritium fuel1. Next was “alpha heating,” where the neutron yield is doubled due to the additional energy deposited in the fuel by alpha particle stopping2,3. Now, we have achieved the burning plasma state4. We will review the new designs and experiments and compare the results with the burning plasma criteria and metrics.

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