Anomalous transport and losses of energetic particles in fusion plasmas

Instabilities can significantly reduce the confinement of energetic particles (EP) thus limiting the performance of fusion devices. In this presentation we study EP anomalous transport and losses in the presence of energetic geodesic acoustic modes (EGAMs) and tearing modes, using the recently developed Toroidal Accelerated Particle Simulator (TAPAS) code. It is shown that even if EGAMs are axisymmetric and non-turbulent, a chaotic channel from the inner region to the edge of the tokamak is created leading to losses of counter-passing EP. Also, numerical evidence is presented of trapping-induced super-diffusion, leading to asymmetric transport and a net toroidal torque. The impact of single-helicity (m=2, n=1) tearing modes on fusion-born alpha-particles transport is also studied including island rotation. In qualitative agreement with previous simulations and observations in TFTR, DIII-D and AUG tokamaks, it is shown that the density profile can exhibit a global modification leading to significant alpha particles losses. This is due to the fact that, although the magnetic field is integrable, the alpha particles can exhibit chaotic dynamics and anomalous exit time statistics.