Exploration of Fusion Plasmas

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• Exploration of Fusion Plasmas
• Using Integrated Simulations
• Jill Dahlburg, Naval Research Laboratory
• Presented by Dale Meade, Princeton University
• With contributions from
• Steve Jardin Princeton University and Doug Post,
  Los Alamos
• from FESAC Integrated Simulation Optimization
  of Fusion Systems) Subcommittee
• Jill Dahlburg, Naval Research Lab (Chair)
  James Corones, Krell Institute, (Vice-Chair)
  Donald Batchelor, Oak Ridge National Laboratory
  Randall Bramley, Indiana University Martin
  Greenwald, Massachusetts Institute of Technology
  
• Stephen Jardin, Princeton Plasma Physics
  Laboratory Sergei Krasheninnikov, University of
  California - San Diego
• Alan Laub, University of California - Davis
  Jean-Noel Leboeuf, University of California - Los
  Angeles John Lindl,
• Lawrence Livermore National Laboratory
  William Lokke, Lawrence Livermore National
  Laboratory Marshall
• Rosenbluth David Ross, UT - Austin and,
  Dalton Schnack, Science Applications
  International Corporation

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Outline of Presentation

• Goals
• Issues and Challenges
• Examples of Current Work
• New Capabilities Required
• Future Plans

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Capabilities Required to Make Progress in Fusion
Science
Diagnostics
Integrated Simulation
Experiments
Theory
Progress in Theory, Diagnostics, Experiments and
Computer Capability make Large Scale Integrated
Simulations Meaningful
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A Tokamak Burning Plasma Experiment (ITER)
Large - 30m tall, 20 ktonne expensive
5B complex first burning plasmas 2018
An international effort (JA, EU, US, RF,CN, ROK)
is underway negotiate a site and cost-sharing
arrangement to build ITER.
Latest news http//fire.pppl.gov
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An Integrated Simulation of Burning Plasmas is
Needed
Burning plasmas are complex, non-linear and
strongly-coupled systems. highly self driven
(83 self-heated, 90 self-driven current)
plasmas are needed for power plant scenarios.
Does a burning plasma naturally evolve to a
self-driven state?
A burning plasma simulation capability would be
of great benefit to Understand burning
plasma phenomena based on existing expts
Refine the physics and engineering design for a
BP experiment Provide real time control
algorithm for self-driven burning plasma, and to
optimize experimental operation Analyze the
experimental results and transfer knowledge
knowledge.
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Elements of an Integrated Tokamak Plasma Model

• Sawtooth region q lt 1
• (MHD and global stability)
• Core confinement region
• (turbulent transport)
• Magnetic islands q 2
• (MHD and global stability)
• Edge pedestal region
• (edge physics, MHD, turbulence)
• Scrape-off layer
• (parallel flows, turbulence, atomic physics)
• Vacuum/Wall/Conductors/Antenna
• MHD equilibrium, RF and NBI physics

Each of these different phenomena can be examined
by an appropriate set of codes. Simplified
models can be produced for use in the Integrated
Modeling code, and can be checked by detailed
computation
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Typical Time Scales in FIRE
Burning Plasma Physics Spans Many Time Scales
SAWTOOTH CRASH
ELECTRON TRANSIT
ENERGY CONFINEMENT
TURBULENCE
CURRENT DIFFUSION
ISLAND GROWTH
?LH-1
??A
??FW
?ci-1
?ce-1
10-10
10-2
104
100
10-8
10-6
10-4
102
SEC.
RF Codes
2D MHD (Transport Codes)
Ion Gyrokinetics
3D Extended MHD Codes
Electron Gyrokinetics
Telescoping in time is necessary because of the
wide range of timescales present in a fusion
device. Not possible to time-resolve all
phenomena for entire discharge time as it would
require 1012 or more time steps.
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Major US Toroidal Physics Design Analysis Codes
Used by Plasma Physics Community





These need to be integrated into one
comprehensive simulation code.
Examples of results follow.
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Example of Present Integrated Modeling Capability
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Present capability TSC (2D) simulation of an
entire burning plasma tokamak discharge
(FIRE) Includes Ohmic heating Radio-Freq Wave
heating Alpha-particle heating Microstability-base
d transport model L/H mode transition Sawtooth
Model Evolving Equilibrium with actual coils and
eddy currents in vessel
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Additional Features are Needed for BP Simulation
2-D Physics including model for density
profile, plasma-wall interaction and pumping
model for edge ion temperature - important for
core transport model model for edge plasma-
turbulence, parallel flow, atomic physics 3-D
Physics including MHD instabilities (local)
- sawtooth, alpha driven, MHD instabilities
(global) - kink - feedback stabilization,
disruption fueling - pellet injection
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The Beginning of Disruption Models
Example DIII-D shot 87009

• Time dependence at disruption onset
• Growing 3-D magnetic perturbation
• Nonlinear evolution?
• Effect on confinement?
• Can this be predicted?

• Increase in neutral beam power
• Plasma pressure increases
• Sudden termination (disruption)

From D. Schnack, 2003 SIAM Conference on
Computational Science and Engineering (Feb. 2003)
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3-D Nonlinear MHD SciDAC Codes

• Two major development projects for time-dependent
  models
• M3D - multi-level, 3-D, parallel plasma
  simulation code
• Partially implicit
• Toroidal geometry - suitable for stellarators
• 2-fluid model
• Neo-classical and particle closures
• NIMROD - 3-D nonlinear extended MHD
• Semi-implicit
• Slab, cylindrical, or axisymmetric toroidal
  geometry
• 2-fluid model
• Neo-classical closures
• Particle closures being debugged
• Both codes exhibit good parallel performance
  scaling.

From D. Schnack, 2003 SIAM Conference on
Computational Science and Engineering (Feb. 2003)
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Computational Challenges

• Extreme separation of time scales
• Realistic Reynolds numbers
• Implicit methods
• Extreme separation of spatial scales
• Important physics occurs in internal boundary
  layers
• Small dissipation cannot be ignored
• Requires grid packing or Adaptive Mesh Refinement
• Extreme anisotropy
• Special direction determined by magnetic field
• Requires specialized gridding

(t Alfven transit lt t sound transit ltlt t MHD
evolution ltlt t resistive diffusion)
Inaccuracies lead to spectral pollution and
anomalous perpendicular transport.
From D. Schnack, 2003 SIAM Conference on
Computational Science and Engineering (Feb. 2003)
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The fusion community is planning an integrated
simulation capability The Fusion Simulation
Project
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Fifteen-Year GoalFusion Plasma Simulator (FPS)
Envisioned to be an integrated research tool
that contains comprehensive coupled
self-consistent models of all important plasma
phenomena that would be used to guide experiments
and be updated with ongoing results. Would
serve as an intellectual integrator of physics
phenomena in advanced tokamak configurations,
advanced stellarators and tokamak burning plasma
experiments. Would integrate the underlying
fusion plasma science with the Innovative
Confinement Concepts, thereby accelerating
progress.
This need was recognized at the 2002 Fusion
Summer Study at Snowmass and in the report of the
FESAC Development Path Subcommittee charged with
identifying the requirements for the production
of electricity from fusion energy in 35 years.
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Fusion Simulator Project Priority is to Support
Burning Plasma Experiments.

• Ray Orbach, Director, DOE Office of Science
• ITER (Burning Plasmas) is the number 1 priority
  project for the US DOE Office of Science.
• Ultra-Scale Scientific Computing Capability is
  the number 2 priority for the US DOE Office of
  Science.
• FSP logic The Fusion Simulation Project is in
  the number 2 priority category supporting the
  number 1 priority
• Develop predictive capability for Burning
  Plasmas

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A Specific Task Control of a Burning Plasma
(ITER)

• Real time control of the burning plasma will
  be essential to meet performance goals and avoid
  operational limits (e.g. disruptions)
• Use hierarchy of models in real time to
  interpret diagnostic data, control plasma
  actuators, feedback and feed-forward control
  algorithm predict plasma response
• Model all aspects of plasma behavior

• Will optimize performance of burning plasma
  experiments
• Will facilitate rapid testing of models and
  theory with real experimental data
• Can unify computational, theoretical and
  experimental fusion communities

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Full Burning Plasma Simulations will Require an
Increase In Computing Speed by 106, possible
by 2015?
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Focused Integration Initiatives
The full extent of the 15-year project is
expected to require on the order of 0.4B.
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Concluding Remarks

• Numerical modeling has advanced to the stage
  where it plays an important role in understanding
  and predicting plasma behavior in existing
  experiments.
• Full predictive modeling of fusion plasmas will
  require cross coupling of a variety of physical
  processes and solution over many space and time
  scales.
• Plans are being made for an integrated fusion
  simulation activity, the
• Fusion
  Simulation Project (FSP).
• Full simulations of burning plasma
  experiments could be possible in the 5-10 year
  time frame if an aggressive growth program is
  launched in this area.
• A Fusion Simulator would have significant
  benefits to the fusion science program and to a
  Burning Plasma Experiment.

Fusion simulation web site http//
w3.pppl.gov/CEMM Talks for this session will be
linked from http//fire.pppl.gov