the problem; the successes; the challenges

THE PROBLEM; THE SUCCESSES; THE CHALLENGES

HPC Users Forum

Houston, TX

April 6, 2011

Lee A. Berry ([email protected])

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


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.


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


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


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


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.


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


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

11 Managed by UT-Battellefor the Department of Energy 04/21/23DBB

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


High Power Radio Frequency Heating of ITER



Energy Loss Is Dominated By Micro Turbulence


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


Wall Street—Money Never Sleeps



The Integrated Plasma Simulator (IPS):A Light-Weight Python Framework



The SWIM Data Portal Has Proven to Be a (Near) Essential Tool for Monitoring/Debugging Simulations


http://swim.gat.com:8080/Simulation of Wave Interactions with MHD (SWIM)


Time Can be Parallelized If We Are Willing to Use Cycles—Parareal : ~6x wall-clock improvement for 6x cycles:


Plasma Turbulence Simulation

Parareal


Plasma-Wall Interactions Are Poorly Integrated: High Heat Fluxes, Erosion, Redeposition ….



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.

the problem; the successes; the challenges

Documents

fusiongrade plasma

fusion auxiliary power

fusion researchhow

franceifp discussion

department of energywe

department of energyiter

hot plasma

don batchelorifp discussion