Evolution of α-particle distribution in burning tokamaks including energy dependent α transport effects

Standard Fokker-Planck codes calculating the alpha-particle distribution function evolution describe the simple balance between the fusion source term and the collision operator neglecting radial diffusion. In the present paper the effects of radial alpha-diffusion have been studied by means of a modified kinetic equation containing loss terms due to alpha-particle and heat transport. Energy dependent transport coefficients are admitted. As a second method, the effect of energy dependence of the spatial alpha-diffusion coefficient is included using a multi group set of alpha-particle continuity equations. We have determined the sensitivity of the alpha-evolution to the energy dependence of a diffusion coefficient D(alpha)(E) for 2 cases: (i) a generic model for an anomalous D(alpha)(E). (ii) D(alpha)(E) corresponding to stochastic ripple losses.