Effective Ion Tail Formation During Startup Neutral Beam Heating in D-³He Plasmas

Formation of an effective ion tail due to neutral beam injection heating during startup in D-³He plasmas is investigated. The main idea is to reduce the energy input required for startup heating as well as the 14-MeV neutron yield by creating an effective tail The optimal beam injection energy and beam species are first estimated by solving the steady-state Fokker-Planck equations for the injected species and for tritons. The startup of D-³He plasma is simulated by simultaneously solving the time-dependent power balance and particle conservation equations together with the Fokker-Planck equations. As a result of tail formation in the fuel ion distribution, both the total input energy and the 14-MeV neutron yield during the startup phase are reduced by ∼20% from the values for Maxwellian plasma.