The Origin of Convecitve Structures in the Scrape-off layer of Linear Magnetic Fusion Devices Investigated by Fast Imaging

The understanding and characterization of turbulence in the scrape-off layer (SOL) of mag-netically confined plasmas is important and may actually be crucial for ITER. The reason being the SOL is the region where the plasma is in direct contact with the first wall. Plasma in the SOL is mainly caused by turbulence radial transport in L-mode discharges and during ELMs in H-mode discharges [1, 2]. We have dedicated several studies to unviel the different facets of turbulence properties in the SOL. In Ref. [3, 4] it was shown that intermittent events are not caused by self-organization of turbulence in the SOL but rather by non-local structures that have large scales and large radial velocities. In order to be precise we called these events avaloids. Later, the universality of avaloids was shown with excellent agreement among four different devices, including the PISCES linear device [5]. The first study of the origin of intermittency in linear devices was done on PISCES where two probes were used [6] one vertical and the other horizontal. It was shown that bursts in the far SOL are correlated to a low frequency mode inside the main plasma column. This article presents the results of our continued effort to have a better understanding of the origin of intermittent structures in linear devices. Indeed, the extrapolation to toroidal con