Simulation and assessment of particle transport in fusion plasmas

Licentiate thesis, 2021

A civilized society need energy to function. An attractive new energy source is nuclear fusion with its abundance of fuel, intrinsic safety and limited environmental impact. Although the concept of fusion for energy has been well understood for over a century, to create it here on earth has been more irksome. The most developed concept for fusion is the tokamak, which is a torodial shaped chamber where a hot ionized gas, a plasma, is confined with a strong magnetic field. Early concepts showed promising results, however later machines showed much larger transport than was expected, this was due to turbulent transport.

The plasma can be described in a number of different ways, fluid or kinetic descriptions. As the particles are confined to the magnetic field lines due to Lorentz force and this process, called gyromotion, is one of the fastest process in the plasma, it is beneficial to average out this motion. This is the basis of gyrofluid and gyrokinetic descriptions. Several different codes have been devolved such as EDWM, TGLF and GENE etc from the fluid, gyrofluid and gyrokinetic descriptions. All these describes the different instabilities which dominates the plasma: the Ion Temperature Gradient (ITG), Trapped Electron Mode (TEM) and Electron Temperature Gradient (ETG).

After introducing the aforementioned descriptions of the plasma we discuss the density peaking of the plasma as it important for the efficiency of a commercial fusion power plant