Complex networks for the analysis of the synchronization of time series relevant for plasma fusion diagnostics

A pair of methods, based on joint recurrence plots and a modified version of cross visibility networks, is proposed for the determination of the efficiency of Edge Localized Modes (ELM) triggering by pellet injection. The main issue in the evaluation of the synchronization between pellet injection and ELM occurrence resides in the fact that ELMs are quasi periodic in nature and therefore, after any pulsed perturbation, if enough time is allowed to elapse, an ELM always occurs. The proposed methods allow the efficiency evaluation on a shot to shot basis and the identification of different phases in a discharge. The performance of the methods is illustrated using JET discharges with the ITER Like Wall (ILW).