Fusion, as a potential source of sustainable energy, has long been at the forefront of numerous studies that combine plasma physics, new technologies, and engineering challenges. To achieve nuclear fusion and extract more energy from the process than is invested, we must maintain the plasma at a sufficiently high temperature and density for an adequate duration of time. Currently, the most promising type of fusion reactor is the tokamak, in which hot fuel is contained by a magnetic field in
a toroid-shaped vessel. One of the main problems associated with this containment method is the significant thermal load of the edge plasma on the walls of the tokamak, making a good understanding and simulation of this area crucial for safe and efficient reactor operation.
In the master’s thesis, we will first introduce the scientific background of fusion and describe the issues with the wall geometry at the level of its components—tungsten monoblocks-which play a significant role in the problem. We will continue by constructing a model for the electric field near the monoblocks, which leads to space-charge in the optical shadow due to the different masses of positive and negative particles in the plasma. After describing the integration of the paths of charged particles in the electric and magnetic fields, and the heat fluxes they cause on the wall, we will also present the results of our own simulations of heat fluxes on the monoblock geometry for various fusion-relevant parameter choices. It turns out that different parameter choices cause very uneven distributions of heat fluxes on the surfaces of the monoblocks, and that space-charge in the optical shadow can play an important role in protecting the first edge of the monoblock from excessive heat fluxes. Our findings emphasize the importance of considering the finite size of gyroradius of charged particles in the plasma and the structure of the reactor wall at the monoblock scale when calculating heat fluxes, as they can otherwise be significantly underestimated.
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