Target gain >1 from inertial confinement fusion implosions at the National Ignition Facility*

Creating a controlled fusion reaction that produces more energy than supplied to initiate it (i.e. target gain >1) is a grand scientific challenge with broad societal implications [1,2]. An outstanding issue for each approach pursuing this goal is creating plasma conditions in which Lawson's criteria[3], where the power of fusion self-heating exceeds all the power losses of the system, and target gain >1 are satisfied. After decades of research and technological advances the first laser indirect-drive inertial confinement fusion[4,5] experiment to satisfy the Lawson Criteria was performed, achieving a target gain of 0.72[6-8].  In this work, we will discuss recent results which utilized a 7% increase in laser energy to drive a 7% thicker target resulting in a target gain of 1.5, marking the first time a target gain >1 has been achieved in the laboratory. In this overview, we will review the results from recent experiments discussing the challenges and the improvements to the target quality, design and laser that were made to enable these results. 

[1] National Research Council, Burning Plasma: Bringing a Star to Earth (The National Academies Press, Washing- ton, DC, 2004). 

[2] National Academies of Sciences, Engineering, and Medicine, Bringing Fusion to the U.S. Grid (The National Academies Press, Washington, DC, 2021). 

[3] J. D. Lawson, Proceedings of the Physical Society. Section B 70, 6 (1957). 

[4] Nuckolls, J., Wood, L., Thiessen, A. et al. Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) applications. Nature 239, 139-142 (1972).

[5] J. Lindl, Phys. Plasmas (1994-present) 2, 3933 (1995). 

[6] H. Abu-Shawareb et al. (Indirect Drive ICF Collabora- tion), Phys. Rev. Lett. 129, 075001 (2022). 

[7] A. L. Kritcher et al., Phys. Rev. E 106, 025201 (2022). 

[8] A. B. Zylstra et al., Phys. Rev. E 106, 025202 (2022).