Domaine : Physique du noyau, atome, molécule
Contrat : Stage
Description du poste :
Losses of particles, i.e. particles escaping the confined plasma, result in heat fluxes on the plasma-facing components (PFCs) of magnetic fusion devices. This phenomenon can result in large fluxes, particularly when the particle being lost are energetic, i.e. are characterized by energies much larger than typical other particles present in the plasma (thermal species). In order to ensure that fusion reactors are exploited in safe conditions, it is important to be able to predict the level of heat flux caused by these particle losses depending on the plasma conditions and on the level of power injected by the auxiliary heating systems. This can be done by following the particles from their initial position in the confined plasma to the location where they impige the PFCs. By sampling several classes of plasma particles and performing the appropriate averages, it is then possible to estimate the relevant heat fluxes.
GCT (Guiding-Center Tracking), a kinetic code developed recently in Aix-Marseille University and CEA Cadarache, can be used for this purpose. It integrates the particle trajectories in 5D (3 positions + 2 velocity components), taking into account the plasma equilibrium, background profiles, and various potential perturbations of the confining magnetic field. WEST, the tokamak currently in operation in Cadarache (France), is characterized by a relatively large level of magnetic ripple caused by the finite number of magnetic field coils, which results in toroidal modulations of the magnetic field. The associated losses (ripple losses) can be fairly large, especially since WEST routinely employs large levels of radiofrequency (RF) heating power which creates substantial energetic ion and electron populations in the plasma. It is therefore crucial to estimate the associated heat flux in high power plasmas.
The internship proposed consists of applying GCT to WEST, and deduce the heat flux on the WEST PFCs. The work will consist in using GCT to estimate the losses depending on magnetic ripple, RF power, plasma scenario... These simulations will be compared to experimental values whenever possible, and then be used to deduce scaling laws, allowing the dependence of the heat flux on the main parameters to be explicitely and rapidly obtained. The outcome is the capability to predict under which conditions WEST is operated in safe conditions, and to optimize the plasma scenarios to minimize ripple losses.
Physicist with a background in high performance computing
Ville : F-13108 SAINT PAUL LEZ DURANCE
Langue / Niveau :
Anglais : Courant