Hot Electron Transport in The Corona of Magnetized Directly Driven Inertial Confinement Fusion Implosions at OMEGA

Measured hard x-ray fluxes above 60 keV from shock-driven implosion experiments at OMEGA are shown to increase by ~1.7x with application of an external 10 T magnetic field compared to unmagnetized implosions. A model for the magnetic field evolution in the corona is derived demonstrating that the applied magnetic field rapidly orients in the ablating plasma flow, becoming normal to the capsule surface by ~250 ps. It is shown that hot-electrons generated by two-plasmon decay (TPD) and stimulated Raman scattering that ordinarily escape the capsule potential and lead to charging, become confined in the coronal magnetic field as in a magnetic mirror. The measured D³He-proton and DD-proton spectra confirm the capsule charge is reduced in magnetized implosions. Similarly, the increase in hard x-ray flux is attributed to the refilling of the mirror loss-cone. OSIRIS particle-in-cell simulations are presented to rule out modifications to the non-linear stage of the TPD instability as the cause for the increased flux of hot electrons onto the capsule.