Project Management, Budgets, Plans, and Summary

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Thrust Discussion
Stellarator Panel Renew Theme 5 19 March 2009
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Proposed Thrust Relationships to Stellarator
Identify the optimum aspect ratio for sustained
high beta operation -Stellarators can be
designed over a wide range of aspect ratios no
physics drive to low aspect ratio Optimization of
steady-state disruption-free plasma confinement
using 3D quasisymmetric magnetic fields -This
is the home thrust for the US stellarator
program supporting vision of TAP ITER-era
goal Achieve high beta fusion confinement using
minimal applied external magnetic
field -Potential contributions here of 3D
shaping/analysis to augment other concepts
Stellarator can provide significant contributions
to proposed thrusts above and cross-linkages to
other theme thrusts
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Optimization of steady-state disruption-free
plasma confinement using 3D quasisymmetric
magnetic fields
Satisfaction of this thrust requires resolution
of the TAP stellarator scientific and technical
questions. Tier 1 issues Improved design and
construction for 3D fields Integrated
high-performance of a quasisymmetric
system Predictive capability with
quasisymmetry 3D divertor design and impurity
control Determination of disruption boundaries
with 3D shaping Let us be clear The TAP report
states

• a quasi-symmetric experiment of sufficient
  scale needs to be undertaken within this
  timeframe to demonstrate, in an integrated
  fashion, that the benefits of quasi-symmetry
  can be extended to high performance, high beta
  plasmas.

The stellarator panel concurs and needs to
develop a program to resolve issues to attain
this goal
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1. Improved Design Construction for 3D fields

• Goals
• Understanding and metrics for drivers of cost and
  complexity in 3D sys.
• Improved designs with increased tolerances,
  reduced assembly costs, easier maintenance (in
  reactor)
• Develop reliable cost and schedule approaches
• Theory Modeling Design
• Improved understanding of physics design
  requirements (e.g. b limits).
• Study of impact of field errors, applicability of
  trim coils
• Integrated detailed design studies to explore
  alternatives and methods
• New Experiments
• Test of improved design strategy resolution of
  outstanding issues

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2. Integrated high performance of QS

• Goals Simultanious HISS04 1.1, beta 5, Ti
  projecting to Ti(0)12keV in reactor, ltTigt6 keV
  consistent with steady state with scalable
  divertor, without disruptions or ELMs.
• Theory Modeling Design research
• Confinement predictability
• Design of suitable configurations
• New experiments
• New QS experiment designed for high beta, low
  collisionality with TiTe.
• gt Sufficient size to shield edge neutrals,
  sufficient flux to confine NBI or RF fast ions.

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3. Predictive Capability with QS

• Goals Predictive understanding of transport vs.
  design and plasma parameters, including effects
  of beta, impurities
• Theory Modeling Design research
• 3D equilibrium models including kinetic effects
• combined turbulence neoclassical Er effects
• non-linear extended MHD models
• Validation of models with experiments
• Existing experiments HSX, LHD, (W7AS), W7X,
  tokamaks
• New experiments
• Low-collisionality high beta QS plasma, with
  flexibility to vary shape, iota
• Method to diagnose flux-surface topology

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4. 3D Divertor Design and Impurity Control

• Goal 3D divertor designs that can handle
  necessary power exhaust, control neutral influx
• Theory Modeling Design research
• Kinetic effects edge turbulence modeling
• More validation of models with experiments
• Integrated design studies with QS configurations
  (using W and liquids)
• Existing experiments LHD, TJ-II?, W7X,
  tokamaks
• New experiments
• Validation experiments for designs of high power
  divertors for QS configurations.

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5. Disruptions

• Goals Understand design requirement to eliminate
  disruptions, e.g. how much 3D shaping is
  required
• Theory Modeling Design research
• Non-linear extended MHD models
• Validation of models with experiments
• Existing experiments CTH, LHD, tokamaks, W7X
• New experiments
• High beta QS experiment(s), with 3D shape and
  iota flexibility

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Progression to ITER-era Goal

• Currently available experiments
• HSX (QS) low beta, CE scale
• Non-QS stellarators at CE - PE scale (LHD, W7X)
• Tokamaks (QS, non-3D) are at PE scale
• ITER (QS) will be at burning plasma/DEMO scale
• Need high beta, low collisionality QS experiments
  to test predictions.
• Alternative Paths
• POP ? PE ? Burning plasma
• POP ITER ? Burning plasma Mitigate risk
  with theory/modeling
• PE ITER ? Burning plasma Mitigate risk
  based on PE stellarators tokamaks.