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The Plasma Control System Simulation Platform (PCSSP) is a highly flexible, modular, time-dependent simulation environment developed primarily to support development of the ITER Plasma Control System (PCS). It has been under development since 2011 and is scheduled for first release to users in the ITER Organization (IO) and at selected additional sites in 2015. Modules presently implemented in PCSSP enable exploration of axisymmetric evolution and control, basic kinetic control, and tearing mode suppression. A basic capability for generation of control-relevant events is included, enabling study of exception handling in the PCS, continuous controllers, and PCS architecture. While the control design focus of PCSSP applications tends to require only a moderate level of accuracy and complexity in modules, more complex codes can be embedded or connected to access higher accuracy if needed. This paper describes the background and motivation for PCSSP, provides an overview of the capabilities, architecture, and features of PCSSP, and discusses details of the PCSSP vision and its intended goals and application. Completed work, including architectural design, prototype implementation, reference documents, and IO demonstration of PCSSP, is summarized and example use of PCSSP is illustrated. Near-term high-level objectives are summarized and include preparation for release of an “alpha” version of PCSSP and preparation for the next development phase. High-level objectives for future work are also discussed. [ABSTRACT FROM AUTHOR]

This paper gives an overview of the scope and context of the CODAC high-level real-time applications (Supervision and Plasma Control) and presents the strategy and current state of design of the tools to support the implementation. A real-time framework, which is currently under development with strong support of the worldwide fusion community will not only support the implementation of plasma control strategies with the extensive exception handling and forecasting functionality foreseen for ITER, but also integrated commissioning, orchestration and supervision as well as the real-time needs of ITER plant system developers. A second cornerstone in the implementation strategy is the development of a powerful simulation environment (Plasma Control System Simulation Platform – PCSSP) to design and verify control strategies, event handling and orchestration and automation. The development of PCSSP is currently under contract and this paper will also give an overview of its current state of development. [ABSTRACT FROM AUTHOR]

In view of the preparation for the operation of the ITER tokamak it is necessary to develop the plasma scenarios taking into account all engineering constraints coming from the plant and including a realistic control system. It is important to consider that, due to the high energy of ITER plasmas, much more stringent requirements are posed on the control of transients in order to avoid machine damage. Several activities are performed in the EU focusing on one side on the scenario optimization from a physics point of view and on the other side on the design and modeling of a realistic plasma control system driving the plasma configuration throughout the whole pulse and suitable for implementation on a real machine. The issues related to the computation of the control feed-forward component are addressed. In particular, the possibility to trigger a feed-forward component to solve controllability problems arising in the transitions from plasma L to H and H to L modes is studied in detail with the support of linear and non-linear simulations. A control strategy is designed and tested on non-linear simulations of the whole pulse, including linear and non-linear effects due to controller switching, plasma shape reconstruction and power supplies. The paper reports on the results of the studies performed and discuss the proposed design of the plasma control system. [ABSTRACT FROM AUTHOR]

Abstract: ITER is targeting Q =10 with 500MW of fusion power. To meet this target, the plasma needs to be controlled and shaped for a period of hundreds of seconds, avoiding contact with internal components, and acting against instabilities that could result in the loss of control of the plasma and in its disruptive termination. Axisymmetric magnetic control is a well-understood area being the basic control for any tokamak device. ITER adds more stringent constraints to the control primarily due to machine protection and engineering limits. The limits on the actuators by means of the maximum current and voltage at the coils and the few hundred ms time response of the vacuum vessel requires optimization of the control strategies and the validation of the capabilities of the machine in controlling the designed scenarios. Scenarios have been optimized with realistic control strategies able to guarantee robust control against plasma behavior and engineering limits due to recent changes in the ITER design. Technological issues such as performance changes associated with the optimization of the final design of the central solenoid, control of fast transitions like H to L mode to avoid plasma-wall contact, and optimization of the plasma ramp-down have been modeled to demonstrate the successful operability of ITER and compatibility with the latest refinements in the magnetic system design. Validation and optimization of the scenarios refining the operational space available for ITER and associated control strategies will be proposed. The present capabilities of magnetic control will be assessed and the remaining critical aspects that still need to be refined will be presented. The paper will also demonstrate the capabilities of the diagnostic system for magnetic control as a basic element for control. In fact, the noisy environment (affecting primarily vertical stability), the non-axisymmetric elements in the machine structure (affecting the accuracy of the identification of the plasma boundary), and the strong component of eddy current at the start-up (resulting in a poor S/N ratio for plasma reconstruction for I p <2MA requiring a robust plasma control) make the ITER magnetic diagnostic system a demanding part of the magnetic control and investment protection systems. Finally the paper will illustrate the identified roles of magnetic control in the PCS (plasma control system) as formally defined in the recent first step of the design and development of the system. [Copyright &y& Elsevier]

Abstract: The plasma control system simulation platform (PCSSP) for ITER shall support the analysis and development of methods to be used by the ITER plasma control system (PCS) for handling exceptions to optimize pulses and assist in machine protection. PCSSP will permit to investigate physical and technical events, such as component failures, control degradation, operation domain excess, plasma state bifurcation or instabilities, and interlock activity. Serving that purpose, the plasma, actuator, diagnostics and PCS simulation modules in PCSSP will be enhanced to compute nominal and off-normal data. Configured by an event schedule, an event generator will orchestrate the activation and manipulate the characteristics of such off-normal computation. In the simulated PCS exceptions will be handled in a pulse supervision layer operating on top of the pulse continuous control (PCC) feedback loops. It will monitor events, decide on which exceptions to respond, and compute new control references to modify PCC behavior. We discuss basic concepts for the event generation in PCSSP, and a preliminary architecture for exception handling in PCS, and show how these will be configured with event and pulse schedules. [Copyright &y& Elsevier]

Highlights: [•] Describes task to develop simulation tool to aid development/testing of ITER PCS. [•] Requirements and use cases and preliminary architecture have been delivered. [•] Detailed design is now being developed. [•] Provides overview of use cases and requirements. [•] Provides overview of architecture and status of development. [ABSTRACT FROM AUTHOR]

Abstract: The active control of plasma discharges in present Tokamak devices must be prompt and accurate to guarantee expected performance. As a consequence, the identification step, calculating plasma parameters from diagnostics, should provide in a very short time reliable estimates of the relevant quantities, such as plasma centroid position, plasma-wall distances at given points called gaps, and other geometrical parameters as elongation and triangularity. To achieve the desired response promptness, a number of simplifying assumptions are usually made in the identification algorithms. Among those clearly affecting the quality of the plasma parameters reconstruction, one of the most relevant is the precise knowledge of the magnetic field produced by active coils. Since uncertainties in their manufacturing and assembly process may cause misalignments between the actual and expected geometry and position of magnets, an analysis on the effect of possible wrong information about magnets on the plasma shape identification is documented in this paper. [Copyright &y& Elsevier]