One requirement for steady state operation in future fusion reactors based on the D(T,n)alpha reaction is an adequate exhaust of the reaction product helium (He). The figures of merit generally quoted for He exhaust capabilities are: 1) the ratio of the global residence time of alpha-particles within the plasma, torr*He, to the plasma energy-confinement time torrE [1], 2) the ratio of partial pressure of He (pHe) in the divertor to that of deuterium (pD2), divided by the ratio of the He and deuterium density in the core (nHe and nD , respectively) . The latter defines the enrichment factor eta