Improvement of the highly energetic passing particle confinement in torsatrons and heliotrons

The configurational effects on the confinement of highly energetic passing particles, especially the helical-field ripple effects, are considered in torsatrons and heliotrons from the viewpoint of increasing the efficiency of tangential neutral beam injection (NBI) heating of plasma. The drift resonances of passing particles (ιΩφ=ΩD, where ι is the rotational transform, Ωφ is the particle toroidal transit frequency, and ΩD is the particle drift frequency) are investigated. It is discovered that the resonant passing particles oscillate poloidally through the variation of the field-line curvature. The passing particles with the energies located in the vicinity of the resonance separatrix are revealed to be as dangerous for confinement, as superbananas are. The existence of the highly poloidally localized resonant particles with lower radial deviations than the corresponding values for the nonresonant particles was found. The particles with the energies close to the state of the high poloidal localization are proposed as the most preferable beam particles for the tangential NBI heating of plasma.