Effects of hydrodynamic motion on the stopping power and energy deposition of alpha particles in an inertial confinement fusion hotspot.

The outflow velocity of expanding deuterium-tritium (DT) fuel can become significant after the bangtime, approaching local ion thermal velocity when the inertial confinement fusion (ICF) hotspot surpasses the ignition threshold. Under such conditions, the conventional assumption of an isotropic target-particle velocity distribution becomes questionable and the influence of bulk fluid motion on alpha-particle transport should be examined. In this paper we derive an analytical expression of the charged-particle stopping power in plasmas with arbitrary bulk fluid motion. We then apply this formalism to alpha-particle transport in an ICF hotspot. The results suggest that incorporating the background fluid velocity into the alpha-particle transport simulation results in a greater fraction of alpha-particle energy being transferred directly to the D and T ions, with a corresponding decrease in the energy deposited to electrons. These results indicate a potentially important correction to alpha-energy deposition in the post-bangtime hotspot.