Progress Towards Steady-State Operation and Real Time Control of Internal Transport Barriers in JET

In JET advanced tokamak research mainly focuses on plasmas with internal transport barriers (ITBs), which are strongly influenced by the current density profile. The formerly developed optimised shear regime with low magnetic shear in the plasma center has been extended to deeply negative magnetic shear configurations. High fusion performance with wide ITBs has been obtained transiently with negative central magnetic shear configuration: HIPB98(y,2)~1.9, βN = 2.4 at Ip = 2.5MA. At somewhat reduced performance electron and ion ITBs have been sustained in full current drive operation with 1MA of bootstrap current: HIPB98(y,2)~1, βN = 1.7 at Ip = 2.0MA. The ITBs have been maintained up to 11s for the latter case. This duration, much larger than the energy confinement time (37 times larger), is already approaching a current resistive time. New real-time measurements and feedback control algorithms have been developed and implemented in JET for successfully controlling the ITB dynamics and the current density profile in the highly non-inductive current regime.
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