Alfven eigenmodes in the RFX-mod reversed-field pinch plasma

摘要

High-frequency magnetic activity has been detected at the edge region of the RFX-mod reversed-field pinch (RFP) device. The analysis, performed by means of an insertable probe measuring the magnetic field fluctuations, shows coherent modes clearly depending on the Alfven velocity, at a frequency in the range 0.1-1.5 MHz. Two main distinct modes are observed, characterized by low (| n | ^ 1) toroidal periodicity, with the features of discrete Alfven eigenmodes. A splitting of the mode frequency is detected, a sign of the relevance of non-linearity in the physical process under study. The experimental observations could suggest an interpretation of the modes in terms of global Alfven eigenmodes. Some hints about the possible drive mechanisms are also given.