The axisymmetric helical field of a tokamak leads to closed unperturbed particle orbits, thus arising as one of the most viable concepts for a fusion reactor. Orbit perturbations due to either Coulomb collisions or electromagnetic potential fluctuations ultimately determine the energy and particle confinement times. Macroscopic temperature and density profiles result from the balance of external sources and of the internally produced fusion power with the transport processes due to the aforementioned mechanisms. Thereby, the numerical design of a commercially viable tokamak fusion reactor requires integration of physics tools that describe both the fast/small scale processes and the slow/macroscopic evolution of the plasma profiles and the plasma shape. To this end, nowadays, progress in the theoretical description of the transport processes allows the application of increasingly realistic theory-based models. This also implies that any modeling activity should be performed keeping into account the assumptions and potential limitations of the models that are employed.
In this talk, first a description of the logical coupling of the tools is given, clarifying the underlying physics of each piece of the system, from the small to the large spatial/temporal scales. Practical applications are then shown. These are based on the ASTRA-SPIDER transport/equilibrium package developed at IPP and in collaboration with TUAP (St. Petersburg), with inclusion of additional modules for turbulence-driven transport fluxes (e.g. TGLF, from General Atomics), and impurity particle transport (STRAHL, developed at IPP).
Finally, an outlook is given on the open challenges in this research activity.
[mehr]