Two-fluid magnetohydrodynamic simulation of confinement of pellet-produced hydrogen clouds in hot magnetized plasmas

The structure of dense particle clouds surrounding ablating hydrogen isotope pellets is investigated, with particular emphasis on the B-perpendicular expansion, ionization, and deceleration dynamics. A time-dependent single-temperature two-fluid one and one-half-dimensional Lagrangian model is used in which the neutral and ionized fluid components are allowed to move with different velocities. The expansion of the Lagrangian cells along the magnetic field lines is also taken into account. For given ablation rates, the confinement radii and the radial distributions of the velocities, particle densities, magnetic field strength, temperature, and other flow and field properties are calculated as functions of the background plasma parameters. The results show that collisional coupling between the neutral and ionized components is strong enough to change the initially spherically symmetric expansion of the neutral particles to a field-aligned, funneled flow pattern, in full agreement with experimental observations. The calculated cloud parameters are compared with measured data and results stemming from earlier single-velocity models.