Shaped tokamak plasmas are unstable to vertical displacements of the plasma column, therefore, requiring active feedback stabilisation. The enhancement of the JET vertical stabilisation system will allow the operation with twice as large Edge Localized Modes (ELMs) than currently possible. This is important in expanding the JET operational space at high current and high shaping; and will allow further exploration and development of the JET operating scenarios with direct relevance to ITER.

In the ELMy H-mode JET scenarios, the baseline operating regime foreseen for ITER, large ELMs can occur with energy loss of up to DWELM~1-2MJ. These scenarios are generally terminated by large plasma disruptions which occur when the response to these large ELMs produces a radial field current excursion larger than the current limit in the Fast Radial Field Amplifier used in the active vertical plasma stabilisation.

The testing and validation of the vertical stabilisation models, observers, controllers and overall design methodology as proposed for ITER will be carried out as part of the proposed enhancement. A demonstration of the performance of such systems through the full range of JET operation and including ELMs of all sizes and types would provide a strong argument for the selection of these control schemes and methodologies for ITER.

A major enhancement of the JET vertical stabilisation system is required in order to further explore and expand the ITER-relevant operating scenarios at JET.

In order to achieve its goals the project has been subdivided into three main tasks:
• Vertical Stabilisation Modelling, Analysis and Controller Design.
• Vertical Stabilisation Controller Hardware and Software
• Vertical Stabilisation Power Amplifier