Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma using LSP*

We present particle-in-cell (PIC) simulations of fast-ion slowing down rates in cool, weakly-magnetized plasma (where $\rho_{e} < \lambda_{De}$ and $v_{fi} > v_{th,e}$) using the fully electromagnetic PIC code LSP. These simulations use explicit algorithms, resolving $\rho_{e}$ and $\lambda_{De}$ spatially and the electron cyclotron and plasma frequencies temporally. Scaling studies of the slowing-down time, $\tau_{sd}$, {\it {versus}} fast-ion charge and background plasma density are in good agreement with unmagnetized slowing-down theory; a small anisotropy is observed between $\tau_{sd}$ in the perpendicular- and parallel-field directions. Furthermore, scaling of the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. The implications of slowing down processes in this regime are described for one magnetic-confinement fusion concept, the small field-reversed configuration device.