Ignition in the laboratory at NIF and routes to higher compression*

Lawson's criterion has been exceeded [H. Abu-Shawareb et al., PRL 129, 075001 (2022)] in Inertial Confinement Fusion (ICF) experiments at the National Ignition Facility (NIF) and gain (G) greater than unity demonstrated. To reach very high gain (G>>1) in ICF requires high areal density (>1.5 g/cm 2 ) assembled via spherical implosion compression to confine the fuel while the thermonuclear burn wave consumes a substantial amount of deuterium-tritium DT-fuel (>10%). Previous ignition experiments are short of this high-gain, high-areal density, requirement, and motivate efforts to understand and improve compression. Experiments to assess the variability in the ignition and burn propagation regime have shown a substantial sensitivity to hydrodynamic instabilities seeded by imperfections in the high-density-carbon (HDC) capsule and to low-mode asymmetries induced by the capsule and delivered laser imbalance. One of the leading hypotheses for degraded compression is the growth of hydrodynamic instabilities during the implosion process, mixing hotter ablator material with the DT fuel and reduce its compressibility. In this talk, we will review recent ignition experiments including attempts toward higher compression in ICF. In one example, we will also show that by beginning with a platform with favorable hydrodynamic stability characteristics (D. S. Clark et al., POP 29, 052710 (2022)), the compression can be substantially increased while maintaining control of instability growth. We are now working to test these features in full scale ignition experiments, ultimately with the goal to increase implosion compression and target gain at the NIF and beyond.