Role of turbulence and electric fields in the formation of transport barriers and the establishment of improved confinement in tokamak plasmas through inter-machine comparison

摘要

Over the past decade new regimes of tokamak operation have been identified, whereby electrostatic and magnetic turbulenceudresponsible for anomalous transport, can be externally suppressed, leading to improved confinement. Although turbulenceudmeasurements have been performed on many confinement devices, the insight gained from these experiments is relativelyudlimited. To make further progress in the understanding of plasma turbulence in relation to improved confinement and transportudbarriers, an extensive experimental and theoretical research programme should be undertaken. The present INTAS projectudinvestigates the correlations between on the one hand the occurrence of transport barriers and improved confinement in theudtokamaks TEXTOR & T-10 and Tore Supra as well as on the smaller-scale tokamaks FT-2, TUMAN-3M and CASTOR, and onudthe other hand electric fields, modified magnetic shear and electrostatic and magnetic turbulence using advanced diagnostics withudhigh spatial and temporal resolution. This is done in a strongly coordinated way and exploiting the complementarity of TEXTORudand T-10 and the backup potential of the other tokamaks, which together have all the relevant experimental tools and theoreticaludexpertise. Advanced theoretical models and numerical simulations are used to check the experimental results.