D.P. BRENNANDEPARTMENT OF PHYSICS AND ENGINEERING PHYSICS
THE UNIVERSITY OF TULSA
PRESENTED AT THE HPC USER FORUMHOUSTON, TEXAS
WEDNESDAY, APRIL 6, 2011
High Performance Computing and the U.S. Burning Plasma
OrganizationNews from the Front Line of Fusion
Simulations
The need for predictive integrated modeling of burning plasmas
Challenge of joining several sub-disciplines with disparate physics
USBPO is an organization dedicated to facilitating burning plasma science, and helps organize and disseminate research
Fusion Simulation Program is a prime example of a nascent community wide integrated modeling effort
The needs of fusion simulation are increasing – need for speed
Summary
Outline
Predictive Modeling Effort in Burning Plasma Science extends from resolving puzzles in current experiments
EXAMPLE: Experiment in the DIII-D tokamak (General Atomics, San Diego) shown, where core instability appears and terminates discharge.
What causes the system to cross into instability, how can we control and prevent this?What are the main drivers?
A combination of HPC, smaller desk top computation, and reduced modeling address these and many other questions.
Predictive Modeling Effort in Burning Plasma Science
Basic onset can be explained, but the evolution to the onset, specific drive through onset, and evolution afterward, all difficult.
Predictive modeling can lead to reduced risk and focused experimental tests.
Accuracy involves coupling between physics drivers
Goals of the Computational Community in Burning Plasma Science
Attain a more profound physics insight of existing experimental results
Test, further understand and extend theory with numerical efforts
Address and resolve issues that stand in the way of ignition in burning plasma experiments
Identify solutions
Predictive modeling of specific experimental configurations in ITER
Provide a basis for analysis of successor experiments such as DEMO
Magnetic fusion codes predict instabilities and other plasma phenomena critical to ITER
“sawtooth oscillations”
Disruptions caused by short wave-length modes interacting with helical structures.
Mass redistribution after pellet injection
Edge Localized Modes Disruption forces, RE, and heat loads during disruption
Interaction of high-energy particles with global modes
S. Jardin (PPPL)
Challenges of fusion simulation
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• Basic description of plasma is 7D– f(x,v,t) evolution determined by nonlinear Boltzmann equation and Maxwell
equations
• Difficulties:– High dimensionality; nonlinearity; sensitivity to geometric details
– Extreme range of time scales (electron cyclotron to wall equilibration): ~ O(1014)
– Extreme range of spatial scales (electron gyroradius to machine size): ~ O(104)
– Extreme anisotropy (mean free path parallel/perpendicular to B field): ~ O(108)
∂f∂t+v⋅∇f +q
m E+v×B[ ]⋅∇v f =C( f)
convection in space
convection in velocity space
Collisional relaxation toward Maxwellian in velocity space
D. Batchelor (ASCAC 06)
Fusion simulation sub-disciplines must be coupled
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Important processes couple all phenomena at all relevant time scales
S. Jardin (PPPL) J.Van Dam (UT)
Integration between and across areas forms key element of this effort to addressed coupled phenomena
Examples: •Heat transport from MHD instabilities•Fast particle transport form MHD instabilities•Fast particle interaction with RF heating•Edge physics coupling with core physics
Specific Example: Edge localized mode coupled to a core MHD mode with energetic particles
What are the stability boundaries and evolution as thermal energy increases and transport changes? => experimental observations
+
xMHD ELM xMHD TM
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PIC f of energetic particles
US Burning Plasma Organization (USBPO)
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Origin: USBPO is national organization of scientists and engineers involved in
researching the properties of magnetically confined burning fusion plasmas
Mission: Advance the scientific understanding of burning plasmas and ensure the
greatest benefit from a burning plasma experiment by coordinating relevant U.S. fusion research with broad community participation
Recent “White Paper on Simulations for ITER” (August 2007) Written by USBPO Topical Group on modeling and simulation Argues that Fusion Simulation Project is an essential element in strategic
planning for fusion energy science in the ITER era Submitted to new Fusion Energy Science Advisory Committee Planning
Panel to identify issues arising in a path to DEMO, with ITER as a focus of that effort
http://burningplasma.org/home.html
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Coordinating the US burning plasma effort
DOE Office of Fusion Energy SciencesSC Assoc DirectorResearch Division
ITER and International Division
US ITER Project OfficeDirector
US ITER Chief Scientist(USBPO Director)
US ITER Chief Technologist
(VLT Director)
USBPO DirectorateDirector
Deputy DirectorAss’t Director for ITER Liaison
Research Committee
USBPO Council(14 members)
Topical GroupMHD Stability
Topical GroupConfinement/Transport
Topical GroupBoundary
Topical GroupWave Interactions
Topical GroupEnergetic Particles
Topical GroupIntegrated Scenarios
Topical GroupFusion Engineering
Topical GroupModeling/Simulation
Topical GroupOperation/Control
Topical GroupDiagnostics
US Burning Plasma Organization
Virtual Laboratory for TechnologyITPA
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Fusion Simulation Project (FSP)
What is the FSP? Computational initiative aimed at the development of whole-device, integrated predictive simulation capability focusing on ITER, but also relevant to major present and planned toroidal fusion experiments
Why is FSP needed? Each pulse in ITER is expected to cost ~ $1M, so a reliable
predictive simulation capability is needed to optimize discharge scenarios and control
Why start it now? Challenging undertaking: will take time to develop, verify, and
validate (V&V) such comprehensive simulations SciDAC program has taken advantage of modern terascale
computing facilities to develop high-performance computational tools to develop new insights into questions of fundamental importance in fusion plasma science
Emerging availability of petascale computing resources
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FSP prototype centers (integration)
Center for Simulation of Wave Interactions with MHD (SWIM) Brings together state-of-the-art extended MHD and RF codes to investigate
the interactions of waves with MHD and the mitigation of instabilities Develop Integrated Plasma Simulator (IPS) framework for coupling of any
fusion code PI: D. Batchelor (ORNL) ORNL, Indiana U, Columbia U, General Atomics, CompX, U Wisconsin, MIT,
NYU, LBNL, Lehigh U, Tech-X Center for Plasma Edge Simulations (CPES)
Develop integrated predictive plasma edge simulation package applicable to burning plasma experiments; integrate edge gyrokinetics with extended MHD
PI: C. S. Chang (NYU) CalTech, Columbia U, LBNL, Lehigh U, MIT, ORNL, PPPL, Rutgers, UC Irvine,
U Colorado, U Tennessee, U Utah Framework Application for Core-Edge Transport Simulations
(FACETS) Multi-physics, parallel framework application for full-scale fusion reactor
modeling; initial focus is core-to-wall transport modeling PI: J. Cary (U. Colorado, Tech-X) Tech-X, LLNL, PPPL, ANL, UCSD, CSU, ORNL, ParaTools, General Atomics,
Columbia U, LBNL, Indiana U, MIT, NYU, Lodestar
The representative suite of tokamak models includes a variety of temporal and spatial discretization schemes
Core Transport: GYRO/NEOCollisional Edge Plasma: BOUT++MHD: M3D-C1, NIMROD
• Explicit PIC Modeling: GTS, VORPAL
• Wave heating, Wall interaction
S. Kruger, J. Cary (Tech-X)
The glue: FACETS - coupling framework for Plasma Simulations
Hot central plasma: nearly completely ionized, magnetic lines lie on flux surfaces, 3D turbulence embedded in 1D transport
Cooler edge plasma: atomic physics important, magnetic lines terminate on material surfaces, 3D turbulence embedded in 2D transport
Material walls, embedded hydrogenic species, recycling
●Coupling on short time scales
● Inter-processor and in-memory communication
● Implicit coupling
S. Kruger, J. Cary (Tech-X)
Fusion simulation “speed” increases due to hardware and algorithms
16 S. Jardin (PPPL)
New features in a burning plasma (1)
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Dominant self-heating (exothermic) Flexibility in present-day experiments to control current, pressure, and
rotation profiles by means of external RF power and neutral beams is dramatically reduced in a burning plasma experiment
High performance requirements Sustained, simultaneous achievement of high temperature and density,
good macroscopic stability, good confinement of plasma energy Robust plasma-wall facing components and diagnostics that can
withstand high heat and neutron wall loadings
•Long pulse length Burning plasma experiment should
have pulse length long compared to the current redistribution time (pulse >> CR) to investigate resistively equilibrated current and pressure profiles in the presence of strong alpha heating
New features in a burning plasma (2)
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Strong coupling The critical elements in the areas of
transport, stability, boundary physics, energetic particles, heating, etc., will be strongly coupled nonlinearly due to the fusion self-heating
Size scaling Due to much larger volume than
present experiments, size scaling becomes important for confinement
Large population of high-energy alpha particles Different behavior from thermal ions Affect stability and confinement
Cross sections of present EU D-shape tokamaks compared
to the cross section of ITER
Full burning plasma simulations will need ~O(106) speed increase
19 D. Batchelor (ASCAC 06)
Summary
HPC is a crucial part of our effort to advance burning plasma science.
Experimental observations/analytic work/small jobs/big jobs steer and make up an HPC burning plasma science effort.
The emerging paradigm involves large scale collaborative efforts to couple together physics models which describe different parts of the puzzle that will predict the outcome of burning plasma experiments.
The USBPO helps to coordinate this community effort to advance our physics understanding of burning plasmas and help make fusion energy a reality.
We live in an exciting place and time, where computational scientists are beginning to collaborate on massive projects to solve long standing puzzles via comprehensive cutting edge simulations.