Plasma rotation in JET.

Plasma rotation is an intensively studied topic within the fleld of fusion/plasma physics. Plasma rotation, the presence of toroidal/poloidal ∞ows in fusion plasmas, is closely related to the ~ E£ ~ B velocity. A shear in this velocity is expected to be a condition for the formation of transport barriers (TBs) due to suppression of instabilities and the decorrelation of turbulent ∞uxes [1]. In JET toroidal plasma rotation, driven by neutral beam injection (NBI), is observed at velocities ranging from approximately 100 to 300 [km/s]. These observations were made using Charge eXchange Recombination Spectroscopy (CXRS), the main diagnostic technique used for plasma rotation measurements at JET. By scaling the found velocities with the thermal velocity a toroidal Mach number is found, a dimensionless quantity comparing the thermal energy and the kinetic energy associated with toroidal rotation of the plasma. In this way the velocities are put into a physical context. The resulting Mach numbers are used to investigate the possibility to characterize plasma rotation observations in JET plasmas.