Tokamak transport phenomenology and plasma dynamic response
The study of the dynamic response of the plasma is a valuable tool for investigating transport processes in a tokamak. A system identification method is developed to estimate the transfer function of the system from the time evolution of its parameters to any excitation. The form of the identified transfer function is linked to a representation of the transport in terms of poles (eigenvalues) and eigenmodes. These eigenvalues and eigenvectors are thus directly deduced from the raw data with no restriction on the underlying processes. There is consequently no need to adjust any simplified transport model to the experimental data. This method is illustrated by analysing the injection of pellets on Tore Supra. The density and the temperature transfer functions were observed to share the same poles with the corresponding eigenmodes, grouped in pairs with identical profiles. This implies the presence of a coupling between the particle and heat flow. A criterion is developed to select amongst the possible coupling mechanisms, based on compatibility with the observed transfer function. The selection suggests a model in which the particle diffusion coefficient depends on the density and the temperature gradient.
Bibliographic Reference: Report: EUR-CEA-FC-1425 EN (1991) 43 pp.
Availability: Available from CEA, Département de Recherches sur la Fusion Contrôlée, Saint-Paul-lez-Durance (FR)
Record Number: 199111294 / Last updated on: 1994-12-02
Original language: en
Available languages: en