摘要:
The performance of tokamak fusion plasmas is heavily linked to the radial heat and particle transport, which is known to be mainly produced by turbulence driven by micro-instabilities. Understanding such processes is thus of key importance for the design and operation of future fusion reactors such as ITER. One of the most commonly used tools to study turbulent transport in the very hot core of tokamaks is gyrokinetic theory, which aims at reducing the physical complexity by averaging out the fast gyromotion, while keeping its averaged effect. The O RB 5 program is a numerical code solving the gyrokinetic Maxwell-Boltzmann system of equations to study various phenomena such as turbulent transport. It is a global particle-in- cell code using a finite element representation with B-spline basis function for the fields and various noise control schemes. The main objective of this work is to improve the performance and physical model of O RB 5 in order to be able to carry out simulations relevant for the Tokamak a Configuration Variable (TCV) at the Swiss Plasma Center. This is done in three major steps. First, the code undergoes a complete refactoring and optimization process with the aim of increasing its maintainability and performance. Using a simple test bed being a simplification of the PIC method while retaining the key elements, various algorithms and parallelization schemes are developed. Furthermore, it is shown that one of the most critical kernels of the PIC algorithm, the charge deposition, can be accelerated by a factor 2.4 in O RB 5. Second, the hybrid electron model, which is used to simulate certain electron modes at a lower numerical cost than the fully kinetic electron model, needs to be corrected. Indeed, in this model, trapped electrons are kinetic while passing electrons have an adiabatic response. This is problematic because it does not satisfy the ambipolarity condition and produces spuri- ous sources of particles and momentum. A corrected model i