Fusion Particles and Neutral Beams in FRC Reactors

We study the interaction of fusion-born particles and neutral beams (NBs) with field-reversed configuration (FRC) plasmas. The power deposited and the current generated are calculated for FRC reactors operating with the D-T and D-³He fusion reactions. In the beam studies we specify the beam energy and current, the injection point, and the impact parameter and include an ionization package to determine the position and velocity of the beam particles when they become ionized. In the case of fusion-born particles, we consider a large number of isotropic particle sources distributed inside the FRC. The plasma equilibria are obtained by solving the Grad-Shafranov equation with a pressure that contains linear and quadratic terms in the flux function. A Monte Carlo code that includes particle drag and diffusion is then employed to follow the exact trajectories of the fusion or beam particles and calculate the resulting current and deposited power. The effect of a rotating magnetic field and a toroidal field on the current and deposited power is also studied. In D-T reactors the current generated by the alpha particles is small, but the deposited power fraction is large, and NBs can produce significant currents with reasonable input powers. In D-³He reactors the fusion protons can produce large currents, but the deposited power fraction and the NB current drive efficiencies are low. A small toroidal field, compatible with high FRCs, reduces the deposited power fraction and the current.