EFDA-JET-CP(08)03/01
Fusion Alpha Performance in Advanced Scenario Plasmas
The fusion reaction rate and, thus, the energy production is strongly dependent on ion temperature and density. Therefore, optimizing these quantities is essential when designing a fusion reactor. However, if the plasma is hot close to the separatrix, lot of energetic particles will escape from the plasma, causing a threat to the first wall. Therefore, the ideal plasma profiles would have a broad hot and dense region around the plasma core, and a cool edge. One way to maintain this kind of profiles is by creating a so-called Internal Transport Barrier (ITB). Traditionally, ITBs are observed in advanced scenario plasmas, characterized by a reversed magnetic shear in the plasma center. Such a reversed q-profile can be created by a low or vanishing toroidal current in the plasma center, which decreases the poloidal magnetic field and, consequently, increases the widths of fast particle orbits.