  An impurity hole observed in the Large Helical Device (LHD) is a hollow
density profile of an impurity ion species formed in the core plasma where the
negative (inward-pointing) ambipolar radial electric field ($E_r$) exists.
Although local neoclassical models have predicted the sign of $E_r$ in impurity
hole plasmas is negative for the entire minor radius, an experimental
measurement of an impurity hole plasma has shown that the $E_r$ changes the
sign from negative to positive along the minor radius. In the present work, we
investigate neoclassical impurity transport in an impurity hole plasma using a
global neoclassical simulation code FORTEC-3D. The variation of electrostatic
potential on flux surface ($\Phi_1$) is evaluated from the quasi-neutrality
condition in multi-ion-species plasma by the global simulation. The ambipolar
$E_r$ and neoclassical fluxes are determined in solving a global drift-kinetic
equation including the effect of $\Phi_1$. By the global simulation, we show
that an $E_r$ which changes the sign along the radius is obtained as a solution
of the ambipolar condition and with such an $E_r$, impurity carbon flux can be
outwardly directed even where $E_r<0$ and the carbon density profile is hollow
around the magnetic axis. Furthermore, it is found that the outward carbon flux
is only a factor 2-3 from balancing the modeled inward turbulent flux. Our
result indicates that we have moved one step closer to reproducing the impurity
transport in impurity hole plasmas by kinetic simulation.
