The properties of alpha-particle confinement of l = 2 stellarat ors have been studied as a function of the aspect ratio (3 < R/a < 12). A collisionless orbit calculation has been performed numerically for stellarator configurations obtained by winding the helical currents on circular-cross-section tori with a constant pitch in toroidal coordinates. All the configurations studied exibit pronounced separatrixlike features that also rotate with constant pitch in toroidal coordinates. The fraction of alpha particles contained within the last closed magnetic surface rapidly increases with the aspect ratio and is >80% for R/a > 4. The escaping alpha particles cross the separatrix within narrow helical strips around the X-point path when it is between the inboard and the top of the torus. The particle motion is also followed outside the last closed magnetic surface. When the boundary (i.e., the surface where the helical currents flow) is sufficiently far from the plasma, the escaping alpha particles are found to remain trapped in the X-point region.
