  A qualitative theoretical approach is proposed for the study of fast ion
behavior in tokamak plasmas with a current hole. For the equilibrium magnetic
configuration in a current hole tokamak we employ a simplified model based on
an analytical approximation of the poloidal flux function shape. For that the
radial extent of the plasma core area with zero rotational transform is used as
a characteristic parameter. The modification of the fast ion orbit topology, as
caused by the current hole, is studied. The model yields manageable analytical
expressions describing completely the current hole effect on the confinement
domains as well as on the boundaries separating the regions of different-type
orbits in the constants-of-motion space. Subject of investigation is the
current hole effect, both on the convective transport of fast ions induced by
their slowing down as well as on the diffusive transport caused by pitch angle
scattering. The influence of slowing down on the distribution functions of
energetic particles (charged fusion products, NBI ions) in current hole tokamak
plasmas is calculated and illustrated. The approach proposed is tested for a
specific JET current hole scenario and the results are compared with numerical
Fokker-Planck predictions.
