Thermonuclear burn wave propagation across an ultrahigh magnetic field

Summary form only given. It had been noticed long ago that the requirements for inertial confinement fusion (ICF) ignition in a cylindrical target can be significantly relaxed if the plasma were compressed simultaneously with the flux of the entrained magnetic field from its seeded value 4100 kG to the peak value of 4100 MG. The ultrahigh axial magnetic field insulates the hot spot from the cold walls compressing it and confines the fusion α-particles. Both approaches to magnetic flux compression by imploding plasmas envisioned in Ref. 1, with pulsed power and laser ablation, have been demonstrated to work, producing peak fields of 42 MG and 36 MG, respectively. Recent numerical simulation results have predicted the possibility of ICF (MAGLIF) ignition and high energy gain in a flux-compression load driven by a next generation fast multi-MA high-current facility. A key issue of producing high fusion energy gain for all options of this approach is the propagation of the fusion burn across the ultrahigh magnetic field, from the hot spot to the cold fuel. Confining the α-particles, the axial field thereby reduces the velocity of burn propagation wave roughly by a factor of ωατα , where ωα and τα are the fast α-particle Larmor frequency and collision time, respectively. We report the results of analytical and numerical modeling of the burn propagation across the ultrahigh magnetic field in DT plasmas at keV temperatures and above solid density. Our study employs a diffusion model for the fast α-particle energy density. We discuss parameter ranges available for ignition and burn propagation when either a pulsed-power facility or a MJ-class laser is used to compress the plasma together with the frozen-in magnetic flux.