Analysis of the impact of driven P1 on implosion symmetry tuning.

Background In laser-driven Inertial Confinement Fusion, achieving spherical symmetry in the implosion of the capsule is crucial for high-gain fusion.

Purpose Full-time symmetry diagnosis and tuning are employed to optimize drive symmetry and suppress fuel perturbations. During the implosion accelerator phase, backlight imaging is typically used to primarily regulate the low-order axisymmetric asymmetries P2 and P4. However, in actual experiments, factors such as laser power and diagnostic holes layout can also lead to the emergence of P1 asymmetry.

Methods This paper investigates the influence of P1 asymmetry on the measurements of P2 and P4 through hydrodynamic simulations coupled with X-ray backlight imaging.

Results The results show that P1 asymmetry causes capsule displacement, thereby generating additional asymmetric signals in P2, P4, and even P3. When P1 reaches approximately 5%, its absolute additional contribution to the fitted P2 exceeds 2%, with a relative error exceeding 10%, indicating that this effect is non-negligible and has a significant impact on P2 measurement.

Conclusions The asymmetric components of various orders exhibit regular variations with P1. Simulation analysis demonstrates that backlight imaging can provide more detailed information on drive asymmetry, thereby aiding in improving the accuracy of symmetry control.