First demonstration of improved yield with increased compression in high-performance implosions on the National Ignition Facility

Creating a controlled fusion reaction, where the self-heating exceeds the power losses long enough for more energy to be produced than used to start the reaction (target gain >1), is a grand scientific challenge with broad societal implications. After decades of research, experiments at the National Ignition Facility (NIF) have demonstrated this for the first time, using the indirect-drive, inertial confinement fusion (ICF) approach [1]. Here, a high-power laser rapidly compresses a small capsule containing the fusion fuel to high temperatures and pressures, thereby initiating fusion reactions. Using up to 2.2 MJ of laser energy, target gains of ~2.4 and energy yields of ~5 MJ have been achieved. However, future applications will require target gains >10, and a major challenge is to improve performance. One approach is to reduce the adiabat and increase compression, although historically increasing compression on a given design did not result in increased performance. We will discuss recent focused experiments to explore the impact of reduced adiabat and increased compression using an optimized shock timing via small changes to the laser pulse. Compared to the baseline experiment [2], the first NIF shot to reach >1 MJ of yield, these experiments demonstrated ~10% increased compression and ~80% increased yield. This design is the only platform to have achieved ignition and gain >1 with a driver energy of <2 MJ. Notably, this is the first time a design has responded with increased performance to a reduced adiabat at the NIF.

 

This work was performed under the auspices of the U.S. Department of Energy by LLNS, LLC, under Contract No. DE-AC52- 07NA27344. LLNL-ABS-851371

[1] H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Letters 129, 075001 (2022)

[2] H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Letters 132, 065102 (2024)