Ripple induced stochastic diffusion of trapped particles in tokamak reactors

The particle-ripple interaction in tokamak plasmas is investigated. It is shown that the destruction of the particle adiabatic invariants can be understood through the resonance overlapping mechanism. The hamiltonian description is applied to describe the motion of the particle and the resonant interaction with the perturbating field. The motion near a resonant surface is discussed. In the low ripple zone, the resonances have the classical island topology and a standard Chirikov parameter is used to determine the stochastic threshold. The radial diffusion coefficient is given. The analysis is applied to fusion products in ITER