the problem; the successes; the challenges
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THE PROBLEM; THE SUCCESSES; THE CHALLENGES
HPC Users Forum
Houston, TX
April 6, 2011
Lee A. Berry (lab@ornl.gov)
Colleagues and Collaborators
special thanks to Don Batchelor
IFP Discussion August 20, 2010
2 Managed by UT-Battellefor the Department of Energy
The Environment of Magnetic Fusion Simulation Is One of Collaboration
Acknowledgements:
Sponsors:
– NSF, DOE (Offices of Science and Advanced Computing)
Collaborators:
– MIT, Princeton Plasma Physics Laboratory, General Atomics, ITER, TechX, CompX, Lodestar, U. of Alaska, Fairbanks, U. Carlos III Madrid, Lehigh, U. Tennessee Knoxville, …
Resources:
– NERSC, NCCS, PPPL, ARSC, ITER, TechX, MIT, GA, …
Theory Program Review
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Nuclear fusion: The Process of Building up Heavier Nuclei by Combining Lighter Ones
It is the process that powers the sun and the stars and that produces the elements.
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We can get net energy production from a thermonuclear process.
We heat a large number of particles so the temperature is much hotter than the sun, ~100,000,000°F. PLASMA: electrons + ions
Then we hold the fuel particles and energy long enough for many reactions to occur.
Lawson breakeven criteria: High enough temperature—T (~ 10 keV). High particle density—n. Long confinement time—.
ne E > 1020 m-3s
Nuclear thermos bottle
T
T
T
T
T
T
TT
TT
TD D
D
D
DD
D
D
DD
= 1 breakeven 10 energy-feasible∞ ignition
Q = Pfusion
Pheating
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We Confine the Hot Plasma Using Strong Magnetic Fields in the Shape of a Torus
Charged particles move primarily along magnetic field lines. Field lines form closed, nested toroidal surfaces.
The most successful magnetic confinement devices are tokamaks.
DIII-D Tokamak
Magnetic axis
Minor radius
Magneticflux surfaces
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ITER: Understand the Science and Engineering for Fusion Power Practicality
500 MW of fusion power, Fusion /Auxiliary Power = 10
Seven party collaboration between EU, US, Japan, China, Korea, India
Sited at Cadarche, France
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ITER: Understand the Science and Engineering for Fusion Power Practicality
500 MW of fusion power, Fusion /Auxiliary Power = 10
Seven party collaboration between EU, US, Japan, China, Korea, India
Sited at Cadarche, France
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The Big Questions in Fusion Research
How do you heat the plasma to 100,000,000°F, and once you have done so, how do you control it?
– We use high-power electromagnetic waves or energetic beams of neutral atoms. Where do they go? How and where are they absorbed?
How can we produce stable plasma configurations?– What happens if the plasma is unstable? Can we live with it? Or can we
feedback-control it?
How do heat and particles leak out? How do you minimize the loss? – Transport is mostly from small-scale turbulence.
– Why does the turbulence sometimes spontaneously disappear in regions of the plasma, greatly improving confinement?
How can a fusion-grade plasma live in close proximity to a material vacuum vessel wall?
– How can we handle the intense flux of power, neutrons, and charged particles on the wall?
Supercomputing plays a critical role in answering such questions.Supercomputing plays a critical role in answering such questions.
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The Computational and Mathematical Challenges Are Substantial
High dimensionality—6D plus time
Large numbers of unknowns 107 >1011
Complex medium
– spatially non-uniform
– anisotropic
– nonlocal
– wide range of physics
– highly non linear Wide range of length scales involved – ~ 100 x L << L, length
scales can interact in localized plasma regions mode conversion
Basic equations are non-symmetric and dissipative
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We have been able to make progress by separating out the different phenomena and time scales into separate disciplines
SEC.
Transport Codes:discharge time-scale
10-10 10-2 104100
CURRENT DIFFUSION
10-8 10-6 10-4 102
CYCLOTRON PERIOD
ce-1 ci
-1
SLOW MHD INSTABILITY, ISLAND GROWTH
ENERGY CONFINEMENT, E
FAST MHD INSTABILITY,SAWTOOTH CRASH
MICRO- TURBULENCE
ELECTRON TRANSIT, T GAS EQUILIBRATION WITH VESSEL WALL
PARTICLE COLLSIONS, C
RF Codes:wave-heating and current-drive
Gyrokinetics Codes:micro-turbulence
Extended MHD Codes:device scale stability
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11
Major U.S. Toroidal Physics Design and Analysis codes (Dahlburg et al, Journal of Fusion Energy, 2001)
2D transportInverse Equilibrium
Linear Stability
M3D
PEST-I,II
FULL
NOVA
BALLOON
ORBITFree Boundary Equilibrium
3D Nonlinear MHD
PEST-III NOVA-K
Ideal Non-Ideal
RF Heating & CD
LSC
CAMINO
TORCH
MHD- + particles
JSOLVER
ESC
TEQEFIT
VMEC2D
PIESStatic Time -Dependent
low-n low-nhigh-n
Linear high-n gyrokinetic
DCON
GATO
Vacuum & Conductors
VACUUM
VALEN
NIMRODVMEC
CORSICA
ONETWO
MARS
TOQ
TORAY
CURRAY
WHIST
TRANSP
TSC
FAR
RANT3D
AORSA
ORION
TORIC
METS
AntennaCQL3D
FP-Code
BALDUR
CORSICA
TSCEQintermediate-n
ELITE
HINST
low-n high-nGS2
Nonlinear Gyrokinetic
GTC SUMMIT
GYRO
Particle-in-cell
global Flux tube
global Flux tube
B2
Plasma Edge
UEDGE EIRENE
DEGAS
neutrals2D plasma
3D plasma
BOUT
denotes parallel MPI code
POLAR2D
BALOOO
Flux tubeGyrofluid
GRYFFIN
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High Power Radio Frequency Heating of ITER
Theory Program Review
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Energy Loss Is Dominated By Micro Turbulence
Theory Program Review
ITG (ion temperature gradient) driven turbulence is the most robust and fundamental microturbulence in a tokamak plasma
Whole-volume, full-f ITG simulation for DIII-D
•XGC1 scales efficiently to the maximal number of Jaguar cores
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Wall Street—Money Never Sleeps
Theory Program Review
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The Integrated Plasma Simulator (IPS):A Light-Weight Python Framework
Theory Program Review
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The SWIM Data Portal Has Proven to Be a (Near) Essential Tool for Monitoring/Debugging Simulations
Theory Program Review
http://swim.gat.com:8080/Simulation of Wave Interactions with MHD (SWIM)
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Time Can be Parallelized If We Are Willing to Use Cycles—Parareal : ~6x wall-clock improvement for 6x cycles:
Theory Program Review
Plasma Turbulence Simulation
Parareal
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Plasma-Wall Interactions Are Poorly Integrated: High Heat Fluxes, Erosion, Redeposition ….
Theory Program Review
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Summary/Observations (mine)
Advances in simulation capability are providing the tools needed to understand fusion plasmas.
Multiphysics simulations (including materials) and GPU-based HPCs are changing the game.
Partnerships of applied mathematicians, computer scientists and physicists are enabling these advances.
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