Large magnetic field generation driven by Weibel instability in laser-ablated single plumes

First-principles kinetic simulations are used to investigate magnetic field generation processes in expanding ablated plasmas relevant to laser-driven foils and hohlraums. Strong filamentary magnetic filaments are found to grow in the corona of single expanding plasma plumes; such filaments are observed to outcompete Biermann-battery generation at sufficiently large laser focal radius, reaching saturation values of ∼ 100 T at National Ignition Facility-like conditions. The filamentary fields result from the ion-Weibel instability driven by relative counter-streaming between the ablated ions and a sparse background population, which could result from a gas prefill in a hohlraum or laser pre-pulse. The filamentation is robust with the inclusion of collisions and grows on a timescale of 100 ps, with a wavelength on the scale of 100-250 μm, over a wide range of background population densities; the instability also gives rise to coherent density oscillations. These results are of particular interest to inertial confinement fusion experiments, where such field and density perturbations can modify heat-transport as well as laser propagation and absorption.