EFDA-JET-PR(03)29
Real-Time Control of the Q-profile in JET for Steady State Advanced Tokamak Operation
In order to simultaneously control the current and pressure profiles in high performance tokamak plasmas with Internal Transport Barriers (ITB), a multi-variable model-based technique has been proposed. New algorithms using a Truncated Singular Value Decomposition (TSVD) of a linearised model operator and retaining the distributed nature of the system have been implemented in the JET control system. Their simplest versions have been applied to the control of the current density profile in reversed shear plasmas using three heating and current drive actuators (neutral beam injection, ion cyclotron resonant frequency heating and lower hybrid current drive). Successful control of the safety factor profile has been achieved in quasi steady state, on a time scale of the order of the current redistribution time. How the TSVD algorithm will be used in the forthcoming campaigns for the simultaneous control of the current profile and of the ITB temperature gradient is discussed in some detail, but this was not yet attempted in the present pioneering experiments.