In fusion experiments, the scrape-off layer (SOL) function as a transit region, where hot plasma ejected from the edge and core region is transported along the magnetic field lines to the walls. This ejection happens primarily on the outboard midplane of the plasma column in form of hot plasma filaments with a finite parallel length. As these filaments enter the SOL they expand parallel with a velocity comparable to the local sound speed.
The thermal velocity of the individual species is given as; Vt=sqrt(T/m). We notice that electron will have a much large thermal velocity than the ions due to its smaller mass. The faster electrons will thus leave the filaments, leaving behind a positive charge density of ions. An outwardly directed electric field will thus be generated slowing the electrons and speeding up the ions. If only one ion species is considered the combined ambipolar velocity will thus be; VA =sqrt((Te+3Ti)/mi).
However, difference ion species, like isotopes of hydrogens as well as heavier ions, have different thermal velocities, again due to the difference in masses. The fast electron will here still escape the filaments setting up a positive charge density of ions but now this electrical field will act differently on the difference ion species.
In this project, the students will create a 1-D particle code, and simulate the temporal dynamics of a large number of both electrons and ions, including different ion species. Each particle act under the influence of a combined electrical field created by all particles. Based on realistic parameters from the ASDEX fusion reactor and for a wide combination of different ions, the parallel distribution of the different species should then be determined.
Forudsætninger
Knowledge of numerical solutions of coupled ordinary as well as partial differential equations.Some knowledge of continuum dynamics, plasma physics, and complex dynamics will be beneficial.
