LLNL Collaboration on NCSX

1
LLNL Collaboration on NCSX

• David N. Hill, Tom Kaiser, Vlad Soukhanovskii,
  Tom Rognlien, and Maxim Umansky
• Lawrence Livermore National Laboratory

• Outline
• Present work divertor design (mapping SOL for
  divertor design)
• Proposed work
• Boundary physics divertor measurements
  modeling
• MSE internal field measurements equilibrium,
  internal currents

This work supports high-priority FY11 research
tasks
This work performed under the auspices of the US
DOE by the University of California, Lawrence
Livermore National Laboratory, under contract
W-7405-Eng-48
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LLNL began looking at boundary physics for NCSX
in 2000

• Internal funding for three years
• Engaged Greifswald W7-X boundary group to assist
  with development of 3D SOL model
• Worked with W7-AS group to apply
  VMEC/MFBE/GOURDON codes to map structure of the
  proposed NCSX coil set
• Began looking at potential diagnostics for SOL
  measurements.
• Very modest OFES funding since 2002
• Focus on mapping structure of SOL plasma as
  equilibrium has evolved
• Focus on mapping SOL to divertor structures to
  support design activies
• Reduced the scope of our collaboration with
  Greifswald to periodic consulting on their 3D
  SOL code

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Field line tracing using MHD equilibrium from
either PIES or VMEC/MFBE determines SOL and
divertor geometry

• Extensive benchmarking activity during FY05-06 to
  compare SOL geometry as determined by PIES and
  VMEC/MFBE equilibrium codes. Some differences are
  observed, but within uncertainties.
• Computed SOL geometry used in deriving conceptual
  design for divertor plates. SOL transport
  simulated by magnetic field line diffusion.

4
LLNL is supporting design of PFCs

• Heat flux is estimated by mapping LCFS field
  lines to divertor targets.
• Field lines are a bit short (higher Te at
  target), but density is higher (lower Te at
  target). Different than Local Island Divertors.
• Do we need the inner target plates during early
  low-power operation?

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Infrared and visible TV cameras can provide
information on 3D SOL structure provided
appropriate viewing geometry.

• Wide-angle tangential views provide outline at
  single cross section.
• Inversions possible with model of LCFS (similar
  to what we do now on DIII-D with recycling and
  ELMs).
• Also possible to generate simulated diagnostic
  images.
• Imaging through most ports will require
  re-entrant optics to obtain desired field of
  view, so most of the cost is related to
  engineering design activities.

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Livermore Is Responsible for Divertor IR Imaging
on DIII-D and Has Used the Data to Validate 2D
SOL models

• IR brightness converted to surface temperature,
  from which heat flux can be derived.
• Heat flux profiles mapped to MHD equilibrium.
• Measurements can be compared with simulations.
  Example shows UEDGE 2D simulation.
• On DIII-D, divertor Thomson (LLNL-GA
  collaboration) provides 2D temperature and
  density to compare with simulation.

2d reconstruction of plasma pressure profile in
detached divertor plasma in DIII-D.
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LLNL Brings Experience Designing, Building, and
Using World-Class DIII-D MSE System to NCSX
Internal Current Profile Measurements.

• MSE routinely used to constrain MHD
  reconstruction of DIII-D plasmas with strong
  current profile modification (Advanced Tokamak,
  Hybrid, Negative Central Shear, Current Holes,
  edge bootstrap currents). DIII-D will not run AT
  experiments without MSE.
• Calibration for precision polarization
  measurements, proper line-of-sight, adequate
  spatial resolution, are key elements to
  successful MHD reconstruction.
• Existing collaborations with U. Wisconsin and
  General Atomics complement strengths of the
  Livermore team.

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BES measurements verify strong RSAE localization
around qmin location
BES measurements verify strong RSAE localization
around qmin location
119346
A
B
MSE q-profile
A
Major Radius (m)
119345
B

• BES makes radially localized measurements of
  density fluctuations
• Combined with MSE, BES data confirm high-n RSAE
  density fluctuations are localized near qmin.

Mike Van Zeeland General Atomics
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Some general comments on collaborations

• Collaborations can bring many benefits to host
  institution
• Unique skills/experience in personnel, new
  hardware capability
• Potentially cheaper and/or more flexible
  workforce
• Free energy and fresh ideas from an external
  without the project perspective
• Collaborations can bring many benefits to the
  collaborating institution
• New funding for people and equipment (as opposed
  to more work for same people)
• Opportunity to expand scope of research, applying
  expertise to new problems
• Increased recognition and invitation to branch
  out further, tackle bigger challenges.
• Some key elements of successful long-term
  collaborations in experimental science
• Fund people instrumentation design support
  (free energy, safety valve, tangible assets)
• Have clearly defined institutional roles for
  collaborating institutions (more than
  individuals)
• Provide professional growth opportunities for
  collaborators and help advertise role of host
  institutions