Alpha-particle physics in tokamaks

Efficient plasma heating by energetic fusion α-particles is a key element of achieving ignition or high fusion gain regimes (Q ≫ 1) in a tokamak reactor. The paper summarizes issues and reviews the latest theoretical and experimental results in the area of energetic particle physics in tokamaks. The discussion includes the classical physics of α-particle heating, effects of perturbations on a single-particle confinement, collective instabilities driven by energetic α-particles, description of the potential α-particle loss channels and their impact on a design of the plasma-facing components in a tokamak reactor. Most of the extrapolations to tokamak reactors are done with the use of ITER parameters and operational scenarios as an example.