Avid readers of Modern Sciences shouldn’t be surprised at this point that we’re covering yet another milestone in the path towards nuclear fusion; we’ve reported on several successes in the field many times before, all towards the holy grail of true plasma confinement. Now, with the help of their 192-strong laser array, the Lawrence Livermore National Laboratory (LLNL)’s National Ignition Facility (NIF) just achieved the long-sought creation of “burning plasma.” Their findings were reported in two papers published in the journals Nature and Nature Physics respectively.
You see, the long-term goal of all these tests and experiments is to create and sustain plasma that’s enough to start a nuclear fusion reaction and keep it going. This is the reason why scientists the world over keep designing and redesigning their containment facilities; they are essentially trying to recreate on Earth what the Sun does out in space every single second.
Thing is, that plasma will definitely be very hot and will need to stay that way in order for it to be self-sustaining. Containing the plasma has been a concern that’s been addressed several times before, with increasing degrees of success using strong magnets to keep the plasma from melting its immediate surroundings. Creating plasma that’s “self-heating,” however, is an entirely different pursuit—and the research team at LLNL may have given us our biggest step yet towards cracking the plasma code.
“A burning plasma is when heating from the fusion reactions becomes the dominant source of heating in the plasma, more than required to initiate or jump-start the fusion,” said Annie Kritcher, co-author of both papers and LLNL physicist, to LiveScience. (Kritcher is the lead author of the paper published in Nature Physics.)
Kritcher continued in the LLNL press release: “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.”
To attain their major milestone, Kritcher and the team used their laser array to shoot kilojoules of energy into a fusion fuel pellet that’s barely a millimeter (0.04 in) across containing some 200 µg (micrograms) of hydrogen that’s rich in neutrons, including its isotopes like deuterium and tritium. It was enough to initiate fusion that lasted not even a second, yet was enough to generate energy output that’s equivalent to 10% of all the energy the Sun throws at our planet every instant.
In total, the fusion reaction generated some 10 quadrillion watts of power; what’s striking, however, is that the plasma they created generated enough heat to overpower the heat injected into the pellet prior to the reaction—a feedback process called “self-heating.” The LLNL team got to this remarkable result through clever redesigns and computational modeling that increased their overall efficiency, in effect “increasing the scale while maintaining high levels of plasma pressure,” according to the same LLNL press release.
Kritcher continued: “We learned where we could and could not trust the modeling and when to rely on semi-empirical models. We also found that keeping the driver pressure up longer relative to the time it takes the target to ‘implode’ was important for maintaining a high plasma pressure. Without this pressure, and enough energy coupled to the hot dense plasma, we would not reach the extreme conditions required for significant fusion.”
The attainment of this self-heating plasma marks the newest milestone for the laboratory in its long quest for nuclear fusion power. Kritcher referred to the moment as a “very exciting time for fusion research,” citing even more improvements to the facility’s instruments and technologies due in part to the results obtained from their remarkable experiment.
The team now refers to their self-heating plasma work a “basecamp” for future fusion experiments. According to Kritcher, the team hopes to use their new findings to explore more in the field of nuclear fusion “through a variety of ideas to increase fuel compression and energy coupling.”
References
- Kritcher, A. L., Young, C. V., Robey, H. F., Weber, C. R., Zylstra, A. B., Hurricane, O. A., Callahan, D. A., Ralph, J. E., Ross, J. S., Baker, K. L., Casey, D. T., Clark, D. S., Döppner, T., Divol, L., Hohenberger, M., Hopkins, L. B., Le Pape, S., Meezan, N. B., Pak, A., … Zimmerman, G. B. (2022). Design of inertial fusion implosions reaching the burning plasma regime. Nature Physics, 1–8. https://doi.org/10.1038/s41567-021-01485-9
- Lavars, N. (2022, January 27). Nuclear fusion milestone creates ‘burning plasma’ for the first time. New Atlas. https://newatlas.com/energy/nuclear-fusion-breakthrough-burning-plasma-first-time/
- Metcalfe, T. (2022, January 26). ‘Burning’ hydrogen plasma in the world’s largest laser sets fusion records. LiveScience. https://www.livescience.com/burning-hydrogen-plasma-record-breaking-fusion-experiment
- Padilla, M. (2022, January 26). Nature paper describes the target and laser designs that achieved a burning plasma at Lawrence Livermore. Lawrence Livermore National Laboratory; Lawrence Livermore National Laboratory. https://www.llnl.gov/news/nature-paper-describes-target-and-laser-designs-achieved-burning-plasma-lawrence-livermore
- Zylstra, A. B., Hurricane, O. A., Callahan, D. A., Kritcher, A. L., Ralph, J. E., Robey, H. F., Ross, J. S., Young, C. V., Baker, K. L., Casey, D. T., Döppner, T., Divol, L., Hohenberger, M., Le Pape, S., Pak, A., Patel, P. K., Tommasini, R., Ali, S. J., Amendt, P. A., … Zimmerman, G. B. (2022). Burning plasma achieved in inertial fusion. Nature, 601(7894), 542–548. https://doi.org/10.1038/s41586-021-04281-w
