Hohlraum Wall Suppression by Pre-Imposed Magnetic Fields

In indirect-drive inertial confinement fusion (ICF) experiments, a pre-imposed magnetic field is used typically to improve capsule performance. We show that it could also improve hohlraum drive conditions by slowing inward-expanding wall motion and delaying on-axis plasma stagnation. Experiments were performed on the OMEGA laser platform to study the impact of a ∼24 Tesla pre-imposed magnetic field on the wall motion of vacuum hohlraums. Self-emission x-ray images indicate that by the end of a 1 ns drive, the pre-imposed field reduced inward jet expansion by ∼50 um. Proton radiographs demonstrate that the pre-imposed field delays on-axis stagnation. 3D HYDRA magnetohydrodynamic simulations support these observations. These results advance our physics understanding of how both self-generated and imposed magnetic fields impact hohlraum wall blowoff and provide insight into an under-explored approach to improving hohlraum drive symmetry in ICF experiments.