New way of seeing laser interactions could advance fusion energy
Electrons revealed details that X-rays alone could not show.
Experts
Alec Thomas
New details of how lasers compress fluids have been revealed by a collaboration led by researchers at University of Michigan Engineering and Lawrence Berkeley National Laboratory. The technique could help scientists and engineers get better at compressing fusion fuel so that it burns like a star.
The experiment, done at Berkeley Lab’s Laser Accelerator Center, shot a powerful laser pulse at an ultrathin jet of water, thinner than a human hair. At the same time, a second laser-driven accelerator let fly a pulse of X-rays and electrons that showed what happened when the laser pulse struck the water jet. By running a series of experiments and timing the imaging pulses differently during each, the researchers were able to piece together the whole interaction.
Previously, the team had tried this with just X-rays to image the interaction, like a really fast and bright camera flash. But that wasn’t enough—their simulations didn’t match what they were seeing in the X-rays. By adding electrons to their imaging toolkit, they found what they were missing: a layer of water vapor formed at the surface of the jet where the laser struck.
With the water vapor acting as a cushion, the laser could achieve more even compression than the team initially predicted. This is important for fusion energy because without even compression, fuel escapes through the gaps, and the reaction fails.
The research was primarily funded by the Department of Energy, particularly through the LaserNetUS initiative.
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The corresponding authors of the study are Mario Balcazar, a recent PhD graduate in nuclear engineering and radiological sciences, and Alec Thomas, a professor in the same department.
Other U-M co-authors are Paul Campbell, Matthew Trantham, Karl Krushelnick, Yong Ma, John Nees and Carolyn Kuranz.
Researchers from Lawrence Livermore National Laboratory, Imperial College London, SLAC National Accelerator Laboratory, and the University of Texas at Austin also contributed to the study.