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The Snowmass Assessment of ITER Ned Sauthoff DOE Princeton Plasma Physics Laboratory APS Meeting Philadelphia, Pennsylvania April 5, 2003
The options considered • IGNITOR, FIRE, and ITER would enable studies of the physics of burning plasma, advance fusion technology, and contribute to the development of fusion energy. • The contributions of the three approaches would differ considerably.
Snowmass’ scientific and technical topics Scientific topics: The study of burning plasmas, in which self-heating from fusion reactions dominates plasma behavior, is at the frontier of magnetic fusion energy science. – effects of energetic, fusion-produced alpha particles on plasma stability and turbulence – the strong, nonlinear coupling that will occur between fusion alpha particles, the pressure driven current, turbulent transport, MHD stability, and boundary-plasma behavior Technical topics: – Plasma support technologies: heating, fuel delivery, exhaust, plasma-facing components, and magnets – Nuclear technologies: remote handling, vacuum vessel, blankets, safety and materials
Contributions – IGNITOR offers an opportunity for the early study of burning plasmas aiming at ignition for about one current redistribution period. – FIRE offers an opportunity for the study of burning plasma physics in conventional and advanced tokamak configurations under quasi-stationary conditions (several current redistribution time periods) and would contribute to plasma technology. – ITER offers an opportunity for the study of burning plasma physics in conventional and advanced tokamak configurations for long durations (many current redistribution time periods) with steady state as the ultimate goal, and would contribute to the development and integration of plasma and fusion technology.
ITER Design Features Central Solenoid Nb 3 Sn, 6 modules Blanket Module 421 modules Toroidal Field Coil Nb 3 Sn, 18, wedged Vacuum Vessel 9 sectors Poloidal Field Coil Nb-Ti, 6 Divertor 54 cassettes Q ≥ 10 and inductive burn of ≥ 300 s, aiming at steady state with Q ≥ 5, average neutron wall load ≥ 0. 5 MW/m 2 and average lifetime fluence of ≥ 0. 3 MWa/m 2
ITER’s physics opportunities • “Capability to address the science of self-heated plasmas in reactor-relevant regimes of small * (many Larmor orbits) and high N (plasma pressure), and with the capability of full non-inductive current drive sustained in near steady state conditions. ” – Self-heated plasmas: Q~ 5 (long pulse) to 10 (pulsed) • “Exploration of alpha particle-driven instabilities in a reactor-relevant range of temperatures” • “Investigation of temperature control and removal of helium ash and impurities with strong exhaust pumping. ” – “Exploration of high self-driven current regimes with a flexible array of heating, current drive, and rotational drive systems. ”
Some ITER Magnetic Control Tools Plasma shaping (single null), error-field and resistive wall mode control coils
Some ITER Auxiliary Plasma Control Tools Control Objective Neutral Beam (1 Me. V) Ion Cyclotron (40 -55 MHz) Electron Cyclotron (170 GHz) Lower Hybrid (5 GHz) (option) pressureprofile control core + off-axis current-profile core control core + off-axis very-localized control less-localized control neoclassical tearing mode control flow control weak?
ITER’s technology opportunities Integration of steady-state reactor-relevant fusion technology: – large-scale high-field superconducting magnets – long-pulse high-heat-load plasma-facing components – plasma control systems (heating, current drive, fueling, . . . ) Testing of blanket modules for breeding tritium
ITER Issues/Concerns at Snowmass • Areas: • the predicted edge-instability-induced-power-loads are at the upper boundary of acceptable energy deposition; control and amelioration is needed. • tritium retention is a concern with carbon-based divertor materials. (much discussion of sawteeth / m=n=1 internal modes / ideal MHD) • These issues are the subjects of continuing R&D.
ITER Development Path An international tokamak research program centered around ITER and including these national performance-extension devices has the highest chance of success in exploring burning plasma physics in steady-state.
Summary • Snowmass concluded that IGNITOR, FIRE and ITER would all produce scientific and technological benefits – their missions are distinct, and were clarified • All 3 approaches have science and technology issues, but NO “SHOW-STOPPERS” : the issues are being addressed by continuing R&D • ITER would advance fusion development by integrating three areas: – burning plasma physics, – advanced tokamak modes aiming at steady-state, and – plasma-enabling and nuclear technologies.