Impact of Self-Generated Magnetic Fields on Hot Electron Transport in Hohlraums*

In Inertial Confinement Fusion (ICF) experiments, high laser intensities drive multiple types of instabilities capable of accelerating electrons to supra-thermal velocities. These hot electrons are especially prevalent in hohlraums, where the high intensities at the Laser Entrance Hole (LEH) can couple very effectively to hot electrons and cause deleterious preheat of the implosion. Past work has shown that the directionality of these hot electrons is influenced by the fill density of the hohlraum, but has only considered ballistic hot electron trajectories in the interpretation. However, as the Biermann Battery mechanism is expected to result in magnetic fields of ~200 kG at the LEH, strong enough to significantly confine hot electrons, the assumption of ballistic hot electron trajectories is most likely incorrect. In this work, a suite of 2D MHD hohlraum simulations are used to determine the impact of these self-generated fields on hot electron transport. It is shown that low fill hohlraums exhibit a severa-fold increase in the fraction of hot electrons hitting the implosion vs hitting the hohlraum wall when the fill pressure is lowered, in line with past experimental results obtained using x-ray imaging