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NCSX Research

NCSX Research. M.C. Zarnstorff Princeton Plasma Physics Laboratory NCSX PAC-7 13 July 2004. Outline. NCSX mission and research issues Expected research phases & topics Required capabilities and R&D Team Preparation. NCSX Design Goals: Combine Best Features of Stellarators & Tokamaks.

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NCSX Research

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  1. NCSX Research M.C. Zarnstorff Princeton Plasma Physics Laboratory NCSX PAC-7 13 July 2004

  2. Outline • NCSX mission and research issues • Expected research phases & topics • Required capabilities and R&D • Team Preparation

  3. NCSX Design Goals:Combine Best Features of Stellarators & Tokamaks Use flexibility of 3D plasma shaping to combine best features of stellarators and tokamaks, synergistically, to advance our understanding of both • Stellarators:Externally-generated helical fields; steady-state compatible; robust stability, generally disruption free. • Tokamaks: Excellent confinement; low aspect ratio – affordable; self-generated bootstrap current and flows Transport Optimization: Quasi-axisymmetry • (Boozer,1983) Orbits & collisional transport depends on variation of |B| within flux surface, not the vector components of B ! • (Nührenberg) If |B| is symmetric in flux coordinates, get confined orbits like tokamak  transport very similar to tokamaks, undamped rotation

  4. NCSX Research Mission Acquire the physics data needed to assess the attractiveness of compact stellarators; advance understanding of 3D fusion science. (FESAC-99 Goal) Understand… • Pressure limits and limiting mechanisms in a strongly shaped 3D plasma • Effect of 3D magnetic fields on disruptions • Reduction of neoclassical transport by quasi-symmetric design. • Confinement scaling with quasi-symmetry; transport barrier formation and reduction of turbulent transport by flow shear control with 3D field. • Equilibrium islands and tearing-modes, including effects of magnetic shear, seed perturbations and ion-kinetics • Effect of stochasticity and 3D shaping on the SOL plasma and power and particle exhaust methods. Compatibility with good core confinement. • Energetic-ion stability and confinement in 3D magnetic fields Demonstrate… • Conditions for high-b disruption-free operation • High pressure, good confinement, compatible with steady state

  5. NCSX Will Have Broad Impact NCSX will make strong contributions to the scientific issues facing MFE: (in terms of the Priorities Panel’s Topical Questions) T1.How does magnetic structure impact confinement?What is the effect of 3D shaping on confinement? Shear? Is quasi-axisymmetry effective? How does it differ from axisymmetry? T2.What limits maximum pressure? Can 3D shaping increase the b limit? Is reversed shear beneficial? What are the limiting mechanisms with 3D fields and how can they be controlled? T3.External control and self organizationHow does 3D shaping affect self-organization of profiles? How high a bootstrap fraction is controllable? Under what conditions are disruptions eliminated? T4.Turbulent transportHow is turbulent transport affected by 3D shaping? Does reversed shear help stabilize turbulence in 3D? How does electron transport depend on local shear and curvature? T5 Electromagnetic fields and mass flow generationHow does flow damping affect zonal flows and turbulence stabilization? Can transport barriers be accessed with quasi-symmetry? T6.Magnetic field rearrange and dissipateHow do shear, pressure, seed perturbations, and ion kinetics affect NTM onset and saturation,in detail? T9.How to interface to room temperature surroundings?How is the SOL and interface affected by stochasticity and 3D shaping? Can the interface and exhaust be improved using 3D effects? T11.Electromagnetic waves interacting with plasmaHow do RF waves interact with plasma in 3D? T12.High-energy particles interacting with plasmaHow does 3D shaping affect energetic-ion instabilities? Can they be stabilized? Can orbit losses of energetic ions be controlled in 3D? T15.How to heat, fuel, confine steady-state or pulsed plasmas?How can we control and fuel a 3D plasma? How much control is required? How can we diagnose the plasma state in 3D?

  6. NCSX Has Many Unique Physics PropertiesNeed to explore experimentally • R/a=4.4 • Strong shaping ~1.8, ~1 • No need for external current drive • Designed to have good flux surfaces at high- and low- • ‘Reversed shear’ for stability • Passively stable at =4.1% to kink, ballooning, vertical, Mercier, neoclassical-tearing modes • Stable for   6% by adjusting coil currents • LHD & W7AS operate well above their linear instability threshold • What will be the b limit for NCSX ?

  7. Normalized Minor Radius ( r / a ) Very good Quasi-Axisymmetry: Very Low effective ripple • H.Yamada, • J.Harris et al • EPS 2004 • New stellarator global scaling finds tE ~ [eeff(r=2/3)]–0.4! NCSX eeff(r=2/3) ~ 0.002! • Low eeff gives low flow-damping; control of Er ,flow-shear stabilization; persistent zonal flows • Reversed shear should stabilize turbulent transport, via drift precession reversal • Does NCSX confinement act like historical stellarators or tokamaks or ?? • Local transport mechanisms?

  8. HSX Quasi-helical symmetry: Less flow damping, Goes faster for Less Drive • Flow driven by biased probe • Quasi-symmetry can be spoiled by powering auxiliary coils (Mirror mode)

  9. NCSX will be a Flexible Experiment Variations from coil currents eeff scan • Wide range of 3D shaping flexibility, for control of physics properties • 9 independent field coil currents • B  2 T • Separate trim coils for control of resonant islands and edge shape • Solenoid for control of toroidal current • NBI power up to 6MW (1.5MW initial) • ICRF power up to 6MW • ECH power up to 3MW • Robust divertor configuration, using flux expansion in elongated cross-section • Full set of diagnostics planned eeff (%) increased & reduced • ref • iota Shear scan

  10. FY-06 FY-07 FY-08 FY-09 First Plasma, CD4 NCSX Research will proceed in Phases 1. Initial operation - warm field map, first plasma 2. Magnetic Configuration Mapping (cryogenic) 3. 1.5MW Initial Experiments 4. 3MW Heating 5. Confinement and High Beta - (~6 MW) 6. Long Pulse – (pumped divertor) • Diagnostic & facility upgrades throughout to match research goals • Phases 3 - 5 may last multiple years. • Expect 18 run weeks in FY09

  11. Research Goals of the Initial Phases • Magnetic Configuration Mapping • Document vacuum flux surface characteristics • Document control of vacuum field characteristics using coil current • 1.5MW Initial Experiments • Explore and establish plasma operating space • Characterize low-power confinement, stability, and operating limits • 3MW Heating • Characterize confinement and stability at moderate power, and their dependence on plasma 3D shape • Test plasma stability at moderate b, dependence on 3D shape • Investigate local transport and effects of quasi-symmetry • Characterize SOL properties for different 3D geometries, prepare for the first divertor design. • Explore ability to generate transport barriers and enhanced confinement regimes.

  12. Initial Phases [  Indicates high priority ]

  13. Research Areas for(3) 1.5MW Initial Experiments [  Indicates high priority ]

  14. Research Areas for(4) 3MW Heating [  Indicates high priority ]

  15. Diagnostic Upgrades Provide Needed Measurements • Upgrading the diagnostics will continue throughout Research Program • Initial (MIE) diagnostics: • Ex-vessel magnetic diagnostics (trapped in structure) • Diagnostics needed for initial research phases: • Rogowskii loop • Fast Camera • e-beam mapping apparatus • Design integration for all planned diagnostics included • See B. Stratton’s talk for diagnostics development plan • Details of development plan (and research plan) will evolve • as NCSX research team assembles • as collaboration opportunities are developed

  16. Equipment Upgrades are Also Necessary • Major elements Phase • Plasma facing components and divertors • partial liner 3 Oct. 08 • full liner, with some plates 4 Aug. 09 • divertor 5 Aug. 10 • Heating systems • second NB-line 4 Aug. 09 • RF or further NBI 5 Aug. 10 • Power supplies • all 9 field-coil circuits + trim coils 3 Oct. 08 • full field 4 Aug. 09 • Data acquisition and control • acquisition upgrades along with diagnostics • pre-programmed WFs 3 Oct. 08 • initial feedback control 4 Aug. 09 • Priorities will be set in response to research results

  17. NCSX Research Preparation Long-term developments preparing for research Ongoing: • Assembly of NCSX Research Team • Physics design and requirements for diagnostics (Stratton, Lazarus) • Edge Modeling; Physics design and requirements for PFCs (Mioduszewski) • Preparation for field mapping (e-beam) (Fredrickson) To start later: • Equilibrium reconstruction analysis • Development of feedback control strategies • Development of comprehensive analysis capability (similar to TRANSP). • Pre-conceptual design of RF test antenna.

  18. Preparation of NCSX Research Team NCSX will be operated as a National & International Collaboration, similar to NSTX • Integrated team, including members from many institutions • Open participation by members, open access to data. Will hold Research Forums in FY2005/06 to • Identify groups interested in developing needed diagnostics • Nucleate the research team • Form initial working groups (4 – 6) • Develop prioritized research plans • Opportunities for collaboration • Plan required resources • Diagnostics, equipment upgrades, researchers Preparatory activities (early FY05) • Work to attract best people to participate • Ensure participation of adequate expertise to achieve goals

  19. Participation by Reviewed Proposals DOE funding of collaborations on NCSX will be similar to NSTX • Independently reviewed proposals • 3-year proposal cycle • Input via Program Priorities letter, identifying • Research topics expected to have high priority, and • Topics thought to be most appropriate for new collaboration e.g. not duplicating existing hardware or ongoing work • However, all topics will be open for collaboration proposals Expect call for first round of diagnostic proposals in FY06 • For funding starting in FY06/07 • Additional calls for diagnostic and participation proposals in FY07 and FY08

  20. Conclusions • NCSX is an exciting opportunity for unique fusion-science research. Have developed outline plans for • Research program • Required diagnostic and equipment upgrades • Preparatory research • Preparation of the research team • Ask your advice on • Research priorities • Pace of research and upgrades • Preparatory activities and Research Forum

  21. 4. Confinement and High Beta

  22. 5. Long Pulse

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