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.
Highlights
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. 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
Examples can be found in disparate contexts, including astrophysical plasmas such as accretion discs [2] and planetary magnetospheres [3], where the destabilizing force is typically of the centrifugal type, and laboratory plasmas [4,5], where the force density typically comes from magnetic pressure gradients
Summary
These scaling laws should be considered as upper boundaries, as any deviation from the pure interchange cross phase between electric field and pressure fluctuations reduces the velocity of the blob with respect to predictions [14,15] These models have been successfully compared with experiment in basic plasmas [16] and extensive characterization work has been made in tokamaks [17,18,19], a direct measurement of the transition between the two regimes remains to be achieved in a fusion relevant plasma. Myra et al [26] predicted this process in a two region model of the SOL using the effective collisionality Λ, Λ
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call