Numerical study of ion acceleration and focusing for integrated ion fast ignition experiments

Fast ignition (FI) is a two-step process that uses nanosecond lasers to compress an ICF capsule, and then uses picosecond, short-pulse (SP) lasers to accelerate either high-energy electrons or ions that heat the core to fusion temperatures. This separation of stages has to the potential for higher gain and reduced symmetry constraints as compared to conventional central hotspot ignition.

To understand the feasibility of FI, we evaluate the current state-of-the-art conversion efficiencies, such as laser-to-particle, transport, energy-spectra and focusing efficiencies, for both electron FI (EFI) and ion FI (IFI). Of particular interest to ion FI, is the ability to focus ions using spherically curved targets. Using particle-in-cell simulations, we investigate the ability to adjust the focus of ions by changing the geometry of the curved targets. We find that adjusting the radius of curvature changes the focal distance of ions. However, this can also be affected by other geometric factors such as the height or the target. We will describe the experimental work planned and supporting simulations. Prepared by LLNL under Contract DE-AC52-07NA27344 and supported by the LLNL-LDRD Program under Project No. 24-SI-003.