Studies on electromagnetic turbulence and edge phenomena in fusion plasmas

The magnetic well depth if one of the principal actors when the stability of a confined plasma is analysed. It is the main stabilising mechanism in the TJ-II stellarator, as this is an almost shearless device. This and TJ-II's ability for changing the currents of its coils make the Spanish stellarator a perfect candidate for magnetic well studies. This thesis presents an exhaustive study on plasma performance and stability under theoretically unstable magnetic well conditions. NBI-heated reproducible plasmas were successfully produced even for the most stability adverse conditions and a link between the Alfén Eigenmodes and magnetic well depth was found. Visible light emission at the plasma edge of the JET tokamak has been studied with an intensified fast visible camera since the installation of its ITER-Like Wall. A method to characterize the evolution of ELMs in the divertor and relate the recorded signal with other diagnostics at JET has been developed. A large Matlab library orientated to treat and share the data produced by the intensified fast visible camera has been made available to the users of this diagnostic.Programa Oficial de Doctorado en Plasmas y Fusión NuclearPresidente: Enrique Ascasibar Zubizarreta.- Secretario: Luis García Gonzalo.- Vocal: Antonio López Fragua