Experimental Validation of a Filament Transport Model in Turbulent Magnetized Plasmas

Abstract

In a wide variety of natural and laboratory magnetized plasmas, filaments appear as a result of interchange instability. These convective structures substantially enhance transport in the direction perpendicular to the magnetic field. According to filament models, their propagation may follow different regimes depending on the parallel closure of charge conservation. This is of paramount importance in magnetic fusion plasmas, as high collisionality in the scrape-off layer may trigger a regime transition leading to strongly enhanced perpendicular particle fluxes. This work reports for the first time on an experimental verification of this process, linking enhanced transport with a regime transition as predicted by models. Based on these results, a novel scaling for global perpendicular particle transport in reactor relevant tokamaks such as ASDEX-Upgrade and JET is found, leading to important implications for next generation fusion devices.

Investigation of scrape-off layer and divertor heat transport in ASDEX Upgrade L-mode

“…High recycling conditions where additional transport mechanisms, e.g. convective filaments[10], become important are not described by the scalings shown here.…”

Blob velocity scaling in diverted tokamaks: A comparison between theory and simulation

“…They can lead to enhanced intermittent heat flux on the main vessel wall, possibly damaging radio frequency antennas and wall tiles and causing sputtering of impurities. [13][14][15] It is generally believed that blobs are the result of the nonlinear saturation of interchange-like instabilities in the edge, with the density fluctuation sheared apart by the E Â B velocity and detached from the main plasma, as observed in JET 16 and in TORPEX, 12 and as described by 2D fluid models, e.g., Ref. 17.…”

The influence of temperature dynamics and dynamic finite ion Larmor radius effects on seeded high amplitude plasma blobs

“…The resulting E × B drift moves the blob radially outward. One particular regime is the so called inertial or resistive balloon- * markus.held@uibk.ac.at ing regime, predominantly emerging when the filament is disconnected from the divertor plates due to high SOL collisionality [13,14], high magnetic shear in the vicinity of the X-point or electromagnetic effects [15]. In the inertial regime the basic blob dynamics are captured by two dimensional models that invoke the cold ion temperature and thin-layer (Boussinesq) approximation [16][17][18].…”