Experimental study of the zonal-flow dynamics in the magnetised plasmas of the stellarator experiment TJ-K (English shop)

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The confinement quality of plasmas in toroidal magnetic fields is mainly limited by the turbulent transport perpendicular to the magnetic field. Zonal flows play an important role in fusion research as they are thought to be connected to the formation of a transport barrier in the edge of the confined plasma. This work concentrates on the investigation of the Reynolds stress drive of zonal flows with its connection to the geometry of the confining magnetic field and the influence of the collisionality. The measurements for this work have been conducted at the stellarator experiment TJ-K in plasmas dimensionally similar to fusion edge plasmas. The low temperatures allow the use of Langmuir probes in the entire confinement region. With a poloidal probe array, consisting of 128 Langmuir probes with 32 probes on each of four neighbouring magnetic flux surfaces, density and potential fluctuations can be acquired with high spatial and temporal resolution on the complete poloidal circumference.