Abstract: In this paper.using Monte-Carlo methods,we have calculated the loss and distribution of the energetic alphas on. the first wall for four groups of plasma parameter. We get conclusions as follows: The collisional diffusion energy loss in slowing-down process is much larger than the drift loss for a parabolic plasma; the energy loss caused by the ripple is proportional to the square root of the ripple; the point of the maximum of the loss energy along toroidal angle on the first wall deviates from the minimum point of the toroidal magnetic field due to the toroidal magnetic field and the direction of the deviation is decided by the direction of the toroidal current; whether the escaped alpha particles bomb at the upper part or the lower part of the first wall depends on the direction of the toroidal magnetic field.

Key words: alpha particle, drift loss, diffusion loss