Simulation studies on alpha-particle-driven current in tokamak reactors

Tani, Keiji; Azumi, Masafumi*

Simulation studies are made for alpha-driven currents in tokamak reactors by using an orbit-following Monte-Carlo code. The finite banana width of alpha particles causes an asymmetry particle trapping and consequently an alpha current is driven by the imbalance of transit particles. The current driven by alpha transit particles (simply referred to as transit current) is greatly enhanced by a collaborative effect of the finite banana-width trajectories and a non-uniformity of alpha particle source. The pitch-angle scattering is also very important for the transit current. Fusion produced alpha particles can drive substantial current to assist the bulk bootstrap current in steady state tokamak reactors.