The Effect of the Accuracy of Toroidal Field Measurements on Spatial Consistency of Kinetic Profiles at JET

Toroidal field coil current measurements presently available at the JET tokamak (Hall probe, Shunt, Rogowski coil and an optical fibre measurement) were investigated over 8 years (2008-2014) in order to explain the radial discrepancy between various electron density and temperature profiles focusing on reflectometry and the electron cyclotron emission (ECE) diagnostics. A 1.21­1.8% difference is found between the optical fibre measurement and the reference magnetic coil current based on the Rogowski measurements that reduces the radial discrepancy by at least a factor of two between diagnostics. Dedicated pulses in different power supply configurations indicate a static current is flowing in the toroidal field circuit (not measured by the Rogowski coils) that can be a result of an interplay between the flywheel generator converter and the static units supplying power to the toroidal field
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