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 situated by simultaneously solving the time-dependant power balance and particle conservation equations together with Fokker-Planck equations. As a result of tail information in the fuel ion distribution, both the total input energy and the 14-MeV neutron yield during the startup phase are reduced by approx 20% from the values for Maxwellian plasma.