Home |  ITER Physics Basis (1999)

ITER Physics Basis, Nuclear Fusion 39 (1999), pages 2137-2638: 501 pages



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Overview and summary



ITER objectives and parameters; IPB authorship and editing; 1998 ITER design and performance projections


Plasma confinement and transport



Projections of ITER performance; empirical scaling; non-dimensional similarity; theoretical turbulence-based models; L-H transition. AT modes


MHD stability, operational limits and disruptions



Ideal and resistive MHD beta limits; neoclassical tearing mode and resistive wall modes; AT modes and MHD stability; density limit(s); disruption effects and mitigation, runaway electrons, fast plasma shutdown


Power and particle control



SOL and divertor modelling in reactor regime, radiation and partial/full divertor detachment, ELMs and ELM effects on divertor, divertor erosion, disruption effects and lifetime. Tritium inventory and retention/removal


Physics of energetic ions



Classical alpha slowdown and ripple loss; collective (TAE, etc.) instabilities; unique TAE aspects of ITER/reactor; thermal impacts on PFCs and FW


Plasma auxiliary heating and current drive



Four methods/energy/frequency regimes: NBI (1MeV, negative ions), FW/IC (70 MHz), LH (5 GHz), EC (170 GHz); implementations in ITER; 2 or more options , 100 MW total needed for EMLy H-mode; additional flexibility for AT


Measurement of plasma parameters



Requirements; priorities for operation and science data; systems and implementation in ITER; R&D needs


Plasma operation and control



Wall conditioning; magnetic and kinetic control, AT control, state-cognizant and advanced MIMO control; standard and advanced operation scenarios


Opportunities for reactor-scale experimental physics



Unique aspects/capabilities of ITER: energetic alpha instabilities; self-heating phenomena; integration of physics basis 'elements' in reactor regime; exploration of reactor-regime AT/SS operation

Chapter 1: Overview and summary (38 pp). Rationale for ITER as a 'next-step' magnetic fusion experiment. Rationale for the ITER Physics Basis. IPB authorship and editors. Overview of ITER design and parameters (circa 1998, R = 8.14 m, I = 21 MA) and anticipated performance. Summary of physics basis issues, status and understanding and uncertainties for projection(s) of ITER performance. Conclusions about 'ELMy H-mode' and 'advanced performance' capabilities. Appendix A: Basis for ITER size, field and current. Appendix B: ITER EDA Agreement Article 1 (Special Working Group 1 recommendations re ITER mission, requirements and design basis).

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Chapter 2: Plasma confinement and transport (75 pp). Physics knowledge in plasma confinement and transport relevant to design of a reactor-scale tokamak. Methodologies for projecting confinement to ITER. Theoretical approaches to turbulent plasma transport in a tokamak. Phenomenology of major energy confinement regimes in tokamaks, including those with edge and internal transport barriers. Focus for ITER on energy confinement in the H-mode edge-barrier regime with the edge-localized MHD modes. Approaches for projection: 1) empirical global scaling laws; 2) non-dimensional similarity; 3) 1-D theory-based modelling codes. Uncertainties in confinement predictions. Empirical scalings for projecting the L-mode to H-mode power threshold. Particle and toroidal momentum confinement and their relation to energy confinement.

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Chapter 3: MHD stability, operational limits and disruptions (139 pp). MHD stability and limits on plasma pressure (beta) and density (density limit). Magnetostatic equilibrium, ideal MHD stability and beta limit. Sawtooth instability, coupling of sawteeth to other MHD, fast-ion stabilization, sawtooth models for ITER. Neoclassical tearing modes and NTM effect on energy confinement and beta limit. Wall and rotational stabilization of ideal and resistive-wall instabilities. Mode locking and effects (m,n) field errors. Edge-localized MHD (ELMs, etc.). MHD and beta, pressure gradient limits in 'advanced performance' plasmas with actively-modified current and shear profiles. Density limit(s): empirical scalings; edge power balance and radiative limits in L-mode plasmas; edge-related limits in H-mode plasmas. Disruptions and disruption effects: Causes, frequency and MHD instability onset; 2) Thermal and current quench. Vertical instability (VDE) and halo currents. Runaway electron formation. Controlled fast plasma shutdown (dissipation of plasma thermal and magnetic energies). Disruption avoidance and effect mitigation. `Integrated' modelling of disruptions and fast shutdown.

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Chapter 4: Power and particle control (79 pp). Summary of fusion reactor power and particle control 'problem(s)'. Divertor and SOL physics bases. Experimental data and empirical understanding of SOL and divertor properties. Radiation, neutral particle and geometry effects. Roles of hydrogenic and impurity species. ELMs and ELM effects on divertor. Divertor and SOL modelling status and recent progress; 0-D, 1-D and 2-D modelling. Fuelling and particle exhaust means. Modelling applied to ITER. Engineering and materials issues. Erosion and divertor target lifetime. Effects of disruptions. Wall conditioning and tritium inventory considerations. Summary and conclusions for ITER.

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Chapter 5: Physics of energetic ions (25 pp). Theory and experimental knowledge of energetic particle effects relevant to design of a reactor scale tokamak. Fusion alphas and energetic ions from rf heating. Single particle effects, classical alpha slowdown and thermalization and toroidal field ripple loss. Collective MHD instabilities (TAE, etc.) generated by energetic alpha particles. New characteristics expected in a reactor-scale device. Possible effects on energy confinement. Overall conclusion: fusion alpha particles will provide efficient plasma heating for ignition and/or sustained burn in a next-step ITER-like device. Major concern: localized heat loads on the plasma facing components produced by alpha particle loss, which might affect their lifetime.

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Chapter 6: Plasma auxiliary heating and current drive (45 pp). Roles for heating and current drive systems: heating through H-mode transition and on to ignition; fusion burn control; current drive and current profile control in steady state scenarios; localized CD for control of MHD instabilities. Need for multiple rf systems plus neutral beam injection to satisfy all requirements and provide experimental flexibility. Candidate systems and frequency/energy regimes: 170 GHz electron cyclotron waves; 40-70 MHz fast (ion cyclotron) waves; 5 GHz lower hybrid waves; 1 MeV neutral beam injection using negative ion beam. Likelihood that two or more systems will be needed/employed in parallel. Selection basis for candidate systems: maturity of physics understanding and operating experience in current experiments and feasibility of technology application to ITER. For each: fundamental physics for heating and CD, status and results in present experiments, key aspects of application to ITER and technology developments required.

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Chapter 7: Measurement of plasma parameters (35 pp). Physics issues of the measurements of the plasma properties necessary to provide both control and science data for ITER. Requirements for measurements. Priorities for device operation and conduct of the the experimental program. Proposed measurement techniques (plasma diagnostics systems) described, with emphasis on implementation on ITER and capabilities to meet requirements. Present status (ca 1998) of the diagnostic program on ITER is provided. Research and development program(s) necessary to demonstrate viability of techniques or their implementation outlined.

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Chapter 8: Plasma operation and control (49 pp). Wall conditioning: hydrogen and impurity control on PFCs, method(s) effective with toroidal field present; removal of co-deposited tritium; long-pulse high-duty factor issues. Plasma control: Magnetic control of shaped vertically-elongated plasmas, flux surface and divertor strike point positioning accuracy, long-pulse issues (integrator drift, ac losses in SC magnets), pro-active role of control in PFC/FW thermal protection. More complex MIMO feedback controllers and algorithms needed; control and plasma theory basis in hand for 'advanced MIMO', but validation tests of 'advanced' controller design basis prudent. Kinetic control (density, rotation, temperature, radiation) in plasma core, periphery and divertor. Methods demonstrated in present facilities, but without limitations, interactions imposed by plasma self-heating. Kinetic control algorithms plasma state dependent, e.g. H- or L-mode. State-cognizant 'adaptive' control required; concepts demonstrated in present experiments; ITER first-of-kind test with burning plasma. Operation scenario: initiation, shape and current development, avoidance of MHD instability during shape/Ip rampup. Basis for OH (V-s) design. Considerations for 'advanced' operation: current/shape ramping to obtain weak/reversed shear plasmas, provision of adequate rotation shear, rf and NB CD for long-term profile sustainment, differences/limitations on present understanding of 'AT' scenarios in the reactor regime. Critical first-of-kind role for ITER as 'reactor AT' development/science-study vehicle.

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Chapter 9: Opportunities for reactor-scale experimental physics (12 pp): A reactor scale tokamak [eg. ITER] plasma will exhibit three areas of physics phenomenology not accessible by contemporary experimental facilities. These are: (1) instabilities generated by energetic alpha particles; (2) self-heating phenomena; and (3) reactor scale physics integration, which comprises the simultaneous integration of diverse physics phenomena, each with its own scaling properties. Selected examples that demonstrate the importance and uniqueness of physics results from ITER for both inductive-driven and steady-state reactor options are given. It is argued that the physics learned in such investigations will be original physics not attainable with contemporary facilities and that, in principle, a reactor-scale facility such as ITER can provide the flexibility to needed to optimize the tokamak approach to magnetic fusion energy.

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