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

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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.