Heating, confinement and extrapolation to reactors

The total amount of heating power coupled to the plasma and the energy confinement time are determining parameters for realizing the plasma conditions suitable for the reactor. Additional heating of tokamak plasma is performed by neutral beam injection and radio frequency heating. Various ranges of frequencies are used for the radio frequency heating. Confinement in tokamak plasmas does not behave classically due to anomalous diffusion. In ohmically heated discharges, at low plasma densities, the energy confinement is proportional to the plasma density and can be expressed by the co-called Neo-Alcator or Linear Ohmic Confinement (LOC) scaling law. The largest confinement is obtained in the absence of edge localized modes (ELM) but this confinement regime leads to non-stationary discharges ending with a tendency of impurity accumulation in the center of the plasma. A new confinement regime has been established at TEXTOR-94, a tokamak with a circular cross-section and equipped with a torroidal pump limiter.