Low-mode drive asymmetries are known as significant performance degradation factors in indirect-drive inertial confinement fusion (ICF) implosions. We propose a two-dimensional (2D) dynamic model to explore the impact of time-dependent low-mode drive asymmetries on the shell asymmetries in acceleration phases of implosions. Since during acceleration, the shell areal density (ρRs) asymmetries are relatively small, we can treat the shell as thin shell pieces with finite mass and infinitesimally small thicknesses, neglecting the angular flows between these pieces. The radial motion of each shell piece is dominated by Newton’s law. Through this model, the evolution of the shell radial velocity vs and the shell radius Rs asymmetries of degree n can be characterized in terms of the drive temperature, time-dependent drive asymmetry of degree n and the average ρRs, vs, Rs obtained from one-dimensional (1D) simulations. The acceleration phases of typical gas-fill capsule and layered DT capsule implosions with P2 or P4 drive asymmetries are explored using this model and validated using both 2D radiation hydrodynamic simulations and available backlit shell distortion measurements. This model gives a useful tool for ICF design, with an advantage of simplicity and speed.

The electron thermal conduction strongly affects the hot-spot formation and the hydrodynamic instability growth in inertial confinement fusion implosions. A harmonic-mean flux-limited conductivity model has been widely used in implosion simulations. In this paper, using the high foot implosion N140520 as an example, we have performed a series of one-dimensional (1D) no-alpha simulations to quantify the impact of different conductivity models including the Spitzer–Harm model, the Lee–More model, and the recently proposed coupled Gericke-Murillo-Schlanges model [Ma et al., Phys. Rev. Lett. 122, 015001 (2019)] with the flux limiter fe ranging from 0.03 to 0.15 on the performance of cryogenic implosions. It is shown that varying fe has a bigger impact on the performance than changing conductivity models. Therefore, we have only performed two-dimensional (2D) no-alpha simulations using the Lee–More model with different flux limiters [Formula: see text] to quantify the effect of the electron thermal conduction on the performance, with single-mode velocity perturbations with different mode numbers L seeded on the inner shell surface near the peak implosion velocity. We find that in both the 1D implosions and the 2D implosions with the same L, increasing fe leads to more hot-spot mass and lower hot-spot-averaged ion temperature, resulting in approximately constant hot-spot internal energy. In addition, the no-alpha yield [Formula: see text] is dominated by the neutron-averaged ion temperature Tn in these two cases. Increasing [Formula: see text] from 0.0368 to 0.184 reduces Tn by ∼15% in 1D and by ∼20% for the 2D implosions with the same L, both leading to a ∼20% reduction in [Formula: see text].