Bochum 2015 – scientific programme

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P: Fachverband Plasmaphysik

P 15: Poster Session - Magnetic Confinement

P 15.4: Poster

Tuesday, March 3, 2015, 16:30–18:30, Foyer Audimax

Curvature dependence of blob dynamics in TJ-K — •Stephen Garland, Mirko Ramisch, and Thomas Hirth — Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie, Universität Stuttgart

Turbulent transport in the scrape-off layer (SOL) is an important area of investigation in magnetic confinement fusion research. Relatively dense and hot, field-aligned, filament-like structures (blobs) have been observed to propagate radially through the SOL in many fusion devices, and contribute significantly to SOL transport. The torsatron TJ-K is well suited to turbulence studies since it operates with a low-temperature plasma, allowing Langmuir probe measurements in the entire plasma volume. Despite the low temperature, investigations are relevant to fusion research due to dimensionless plasma parameters similar to those in the edge region of fusion plasmas.

Blob dynamics have been studied in the SOL of TJ-K using a 2D movable probe and the conditional averaging technique. In addition, emissive probes have been used to determine equilibrium electric fields, allowing the calculation of background ExB flows. Experimentally deduced centre of mass radial and poloidal blob velocity components have been compared to an analytical blob model, which has been simplified to express blob velocity in terms of the magnetic field curvature vector. Experimental radial blob velocity components compare well to the model, confirming the normal curvature drive of blob polarisation. On the other hand, poloidal velocity components are comparable to the model only when background ExB flow is also taken into account.