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This document outlines the Integrated Modelling program in ITER, discussing the roles of integrated modelling, plasma operations support, plasma research support, and the plasma simulator for the PCS. It also covers the elements of the CODAC architecture and provides a summary of the ITER Risk Assessment.
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Integrated Modelling in ITER W.A. Houlberg ITER Organization EFDA ITM Task Force General Meeting Lisbon, Portugal 13-17 September 2010
Outline • IM Programme • Roles of Integrated Modelling • Plasma Operations support • Plasma Research support • Plasma Simulator for the PCS • IMAS and PCS elements of the CODAC architecture • Contract for IM infrastructure design • ITER Risk Assessment • Scientific risks • Summary • Supplementary material on ITER Risk Assessment – Scientific Risks
Roles of Integrated Modelling • Applications of IM in ITER can be classified as either Plasma Operations support or Plasma Research support to identify more clearly the requirements, responsibilities, and users (customers) • Plasma Operations support: • IO has primary responsibility for development/adaptation and management – Integrated Modelling Analysis Suite (IMAS) • Available to all ITER Parties • Links to more extensive set of physics components and computing resources of the ITER Parties to enhance physics basis for planning • Plasma Research support: • ITER Parties have primary responsibility for development and validation of improved models • Many extended physics elements will remain proprietary (developmental) • Both areas require extensive collaboration between the IO and ITER Parties: • Further definition • Identification of candidate components and technologies • Implementation
Plasma Operations Support • Operation-driven modelling applications applied to each ITER pulse: • Pulse planning, execution, and plasma reconstruction • Infrastructure and basic features are to be developed and tested during the construction phase and will be available prior to the first experimental campaign • Physics content will evolve throughout the ITER experimental programme *Employs IM tools, **Employs systems tools, ***Physics Team evaluation
Pulse Segments • Extension of present plasma scenario modelling efforts: • More rigorous physics and systems validation required • Pulses are comprised of segments • Identification of fault amelioration techniques • Control consistent with PCS • Not every pulse needs a full simulation from initiation to termination for validation, e.g.: • Standard breakdown and plasma formation (initiation) as initial conditions • Standard ramp-up to flat-top as initial conditions • A combination of segments known from previous operating experience, supplemented by modelling • Standard termination
Pulse Planning • Segment Simulation: • Derived from ITER’s long pulse capability • Each segment may assess a different set of conditions • Slow evolution of the toroidal current profile may create inter-dependence • Pulse Assembly: • Assumes the plasma in each segment independent of history • Include options (variations) for the operator to implement • Physics Validation: • Characterize uncertainty in the simulations • Can the PCS manage the plasma? • Output is a dataset of plasma parameters, demands on each component of the system, required diagnostic systems • Pre-Campaign System Validation: • Check whether systems demands are within expected machine capabilities (CODAC tools) • Organize pulses into daily campaigns: • Should be many more pulses than can be executed • Daily System Validation (repeat of Pre-Campaign System Validation)
Pulse Execution • Real-time (low latency) reconstruction: • Integral to successful execution of ITER pulses • Required for operation of the PCS in controlling the plasma • Displays of the evolution of plasma conditions and behaviour during a pulse • Live reconstruction (latency ~seconds): • Plasma reconstruction integrating results from several diagnostics for control room display superimposed on expected performance from the pulse file • Provides evaluation of the fidelity of the pulse planning, indications of unexpected behaviour, and guidance to the operator • Real-time and live reconstruction may have much overlap • Time slice analysis can provide further guidance to the operator • Forecasting (faster than real-time, long-term goal): • Launching a predictive simulation with a set of proposed actions plus initial conditions from present state • Reveals whether operating bounds may be exceeded by proposed actions • Forecasting tools must progress through validation tests
Plasma Reconstruction • A primary requirement for effective interpretive analysis of experimental results: • Automated system for integrated results from multiple diagnostic signals into a set of physically consistent parameters and profiles and error bars: • Generally an iterative process, constraints on time vs accuracy • May require corrections due to re-calibrations or other corrections from individual diagnostics • Higher levels of reconstruction: • Interpretative analysis of the plasma transport properties, generally requires models for the sources of particles, energy, torque and current drive, which cannot generally be measured directly, i.e. they require reuse of some of the same components used in predictive modelling • Data mining: • Searches for common characteristics • Determining operating limits from prior operation relevant to pulse validation • Detailed physics analyses, retuning of control algorithms and operation constraints, model validation and model improvement • Provides the connecting loop with the Plasma Research Support that enhances preparation for future sessions
Plasma Research Support • Design and upgrade studies: • Opportunities for design decisions diminishing, upgrade options will have to be evaluated over the longer term (see ITER Research Plan) • Scenario and campaign development: • Commissioning and scientific exploration plans in support of the IRP • Heating, fuelling and current drive strategies • Performance optimization within operational boundaries • Experiments that focus on specific physics issues • Identification of experiments on present facilities to validate model features • Model validation: • Until ITER begins operation, the only data available for model validation is produced by presently operating facilities in the domestic programmes • Model improvement: • Improved fidelity (renormalization, addition of missing physics) • Computational efficiency (note severe restrictions on clock time in many areas of operations support)
IM Infrastructure Contract and Team • Purpose: • Design and assist in the implementation of a physics modelling and data analysis infrastructure to support ITER plasma operations and research • Features/status: • Three-year contract • Nominally 2 man-year/year effort • Financial commitments made only through Task Orders • In final negotiations of contract • CEA-led consortium: • CEA/IRFM, EPFL-CRPP, Chalmers University, MIT-PFSC, AREVA TA • Team has breadth and depth of experience in designing modern IM infrastructure • But ITER IM applications are significantly broader than covered by ITM effort (or any similar modernization efforts on the domestic programmes) • First year effort broken down into 6 Tasks
1st Year Tasks • Task 1 – Establish Strategic Requirements: • Establish a list of Strategic Requirements and Use Cases of the various parts of the IM infrastructure • Task 2 – Establish Detailed Requirements: • Refine Strategic Requirements to a more detailed / technical level that allows starting the next phases • Task 3 – Survey technologies / software: • Exploratory phase to investigate the most relevant concepts / technologies to meet the requirements defined during Tasks 1 and 2 • Task 4 – Establish global conceptual design (concurrent with 3): • Draft the global conceptual design of the IM infrastructure (organization chart of the IM infrastructure elements, their links and their functionalities), indicating how it fulfils the Strategic Requirements and Use Cases • Task 5 – Complete conceptual design: • Complete conceptual design, including candidate technologies, implementation schedule, assessment of resources, implementation of the main use cases • Task 6 – Validate conceptual design: • Finalize the report
Plasma Simulator for PCS • Prototype application: • Features of advanced codes: core, SOL, divertor, free boundary MHD • Initial simplified source and transport models with extensibility • Links to DBs for plasma data, system characteristics and constraints, PCS • User interface development
Plasma Simulator • Development of a Plasma Simulator as an initial application: • Supports PCS testing of control algorithms • Provides a prototype application for development of the IM infrastructure • Can employ elementary plasma models for fast turn-around of initial test cases • Attention to extensibility will allow the PS to incorporate the comprehensive physics required for pulse simulation: • Modularity • Free boundary equilibrium • Full set of transport equations • Advanced CS methods (e.g. parallelization, grid computing) • Core, SOL, divertor and PWI • Coupling to the PCS in pulse simulation mode would: • Provide validation the that the PCS can control the pulse • Eliminate the need to employ approximations to the control system that are typically employed in predictive modelling codes • Dynamic coupling to the systems validation tools may also be envisioned
IMAS and PCS Elements of the CODAC Architecture IMAS PCS • The physics elements are only a small part of ITER operations and control
Website Development • Effective communication between the IO and ITER Parties is critical to ITER’s success • Developments in 2010: • FST Department website • ITPA Public, Restricted sites • Project sites • Hundreds of meetings • Thousands of documents • >600 users
ITER Risk Assessment – Scientific Risks • The Reliability, Availability, Maintainability & Inspectability (RAMI) analysis: • Provides an estimate of the overall availability of the ITER tokamak and its ancillary systems for experimental studies • Establishes a framework for the development of the experimental programme • ITER operations schedule is predicated on assumptions about the efficiency of its experimental programme – that the ITER relevant physics will follow the predictions formulated from the physics basis derived from current tokamaks • The rate of progress in ITER’s experimental programme is therefore subject to a variety of uncertainties that give rise to risks of delays or failure to meet the principal mission goals within the timescale desired • Risks to the scientific programme: • Limitations in experimental techniques or deviations in plasma behaviour from predictions • Potential consequences for operation • Possible mitigation measures • Focus on factors related to experimental techniques and plasma physics • Assessment of installed hardware is dealt with in the RAMI analysis and in the ITER Risk Management Plan (see e.g. ITER_D_2YR5P3)
Scientific Risk Assessment R&D Needs • Top 12 risks associated with plasma operation and their potential consequences have been identified, and mitigation strategies (and implications) have been developed: • Disruption mitigation has limited effectiveness • H-mode power threshold at high end of uncertainty range • ELM mitigation schemes of limited effectiveness or require extensive R&D in ITER programme • Vertical stability control limited by excessive noise (or failure of in-vessel coils) • Lack of reliable high power heating during non-active phase of programme • Acceptable “divertor” performance with tungsten PFCs proves difficult to establish over required range of plasma parameters • Level of toroidal field ripple degrades plasma performance • Lack of plasma rotation leads to a degradation of plasma performance • High levels of tritium retention require more frequent tritium removal procedures than foreseen • Incompatibility of core plasma requirements for Q=10 with radiative divertor operation • Inability to achieve densities near Greenwald value required for Q=10 • Inadequate particle control to retain high-Q plasma scenarios
Scientific Risk: Inadequate Disruption Mitigation • Risks: • DMS has inadequate performance in mitigating heat loads or runaway electrons • Consequences of DMS use excessive (e.g. first wall melting, long down time) • Inadequate prediction capabilities • Research Plan Implications: • Limitations in maximum current and fusion power • More frequent shutdowns to replace in-vessel components • Excessive number of uncontrolled disruptions leading to loss of operational time and slower progress in scientific programme • Mitigation: • Focused R&D on DMS-related experiments in present devices and development of validated models – also contributes to improved disruption predictive capability • Possible mitigating measures related to ITER operation, and consequences: • More cautious approach to scenario development – delays in programme • Additional time allocated to R&D on DMS in ITER programme and implementation of upgrades – delays in programme • Limitations on plasma current and fusion power – consequences for mission
Summary • Modelling will be incorporated into the ITER operation and research programme to a far greater extent than is employed in present facilities: • Proposing experiments • Control • We also must contend with a far more diverse and distributed user community • Development of the ITER Integrated Modelling Analysis Suite (IMAS) will address these requirements, but will need significant input from the potential users to ensure its utility and integrity • The efforts of the ITM in anticipating and addressing these needs are greatly appreciated, but we still have a long journey ahead • Thanks to Rui Coelho and his team for hosting this ITM meeting (and his display of Maître d’Hôtel capabilities par excellence)
