A 3-D Cross-Beam Energy Transfer Model for Direct-Drive ICF

In direct-drive ICF, 3D effects in the laser drive can significantly degrade the implosion performance. Low mode, hydrodynamic perturbations can lead to un-stagnated flows at peak compression and an inefficient conversion of kinetic to internal energy. Cross-Beam Energy Transfer (CBET) can also strongly modify 3D asymmetries in the laser absorption [1].

In this talk we will present the development of a laser ray tracing package in the 3D radiative-hydrodynamics code CHIMERA. An inverse projection algorithm for ray initialisation has been implemented, which significantly reduces noise in the energy deposition. A 3D CBET model has also been developed. We will present results from simulations of direct-drive implosions on the OMEGA laser using 1D hydrodynamics coupled to a 3D ray trace and the CBET model. We will also study the effect of enhanced beam mode asymmetries due to CBET in fully 3D calculations. Initially we will examine the how the ablation-phase growth of these perturbations varies with the beam-target ratio, with a long-term view to understanding the unexplained source of yield degradation which has been highlighted by recent statistical modelling campaigns [2].



[1] – A. Colaïtis et al., JoCP 443, 110537 (2021)

[2] – V. Gopalaswamy et al., PoP 28, 122705 (2021)