Developing Predictive Capability for High Performance Steady State Plasmas

ReNeW 

Developing Predictive Capability for

High Performance Steady State

Plasmas

P.
 Snyder,
 A.
 Kritz,
 R.
 Budny,
 C.S.
 Chang,
 M.
 Greenwald,
T.
Carter,
J.
Wright,
G.R.
Tynan


ReNeW 

Primary Goal

Reduce Time to and Cost & Risk Of 1) ITER-experiments

ReNeW 

Secondary Goals: Make Nearer

Term Contributions

•  Provide Deeper Physics Insights to

Experiments

•  Test Theory using Numerical Experiment

•  Help Resolve Serious Performance Issues

•  Scenario Modeling for ITER

ReNeW 

Approach:

•  Identify Key Issues w/ Existing Theory,

Modeling & Experiment

•  Develop Suitable Numerical Models

Capturing Essential Physics

•  Scientifically Validate Simulations Across

Range of Experiments

•  Use Validated Models to Attempt Prediction

of New Experiments

ReNeW 

Caveat Emptor:

•  Recognize we will be extrapolating, not

merely interpolating

•  May require new theoretical insights e.g. to

couple disparate spatiotemporal scales & physics => Not just bigger, faster codes

•  Will still require reduced models for some

problem elements

– Particularly for incorporation into real-time

ReNeW 

Approach:

•  Develop Case Studies

•  Sort Based Upon Impact on DEMO Device

•  Hear ReNeW workshop presentations &

read whitepapers

•  Develop outlines of Predictive Modeling

ReNeW 

Sorting Methodology: What is

Impact of the Prediction?

•  Critical Impact: Results influence machine

health and/or safety issues

•  Performance Impact: Results influence

HPSS plasma performance

•  Ancillary Impact: Results influence non

ReNeW 

Case Studies put forward by Panel

•  Pedestal & ELMs

•  Edge/SOL/PWI

•  Disruptions

•  Core Transport & MHD

•  RF CD & Heating

•  Energetic Particles

ReNeW 

Case Study Organization

•  Scientific & Technical Issues

•  Challenges

ReNeW 

Pedestal & ELMs: S&T Issues

•  Physics of L-H, H-L transitions; threshold

physics

•  Pedestal structure mechanisms

•  Particle & Power loading to PFCs w/ ELMs,

between ELMs

•  ELM Control or Mitigation Scheme

Development

ReNeW 

Pedestal & ELMs: Challenges

•  L-H transition trigger, quantitative P_LH

predictions

•  Pedestal growth to ELM onset

•  Inter-ELM simulations w/ realistic

integrated elements (sources, PMI,…)

•  ELM Mitigation Physics (pellet pacing,

RMP, …)

ReNeW 

Pedestals & ELMs: Research

Program Elements

•  Theory: Possible new approaches that side-step scale

separation assumptions?

•  Computation: Need models for complex edge/SOL

geometry, linking w/ PMI, Neoclassical, MHD &

Turbulence. Is GK sufficient? Full Vlasov Required? How to evolve mean profiles w/ these physics included? Push simulations towards low collisionality, high

Greenwald fraction, opaque to neutrals, small rho-star, high beta-N

•  Experiments: Improve diagnostics on existing devices

(e.g. fueling sources, Bdot, J_|| , high res profiles,

transport fluxes); pedestal studies on new long –pulse devices; Adequate run-time & data analysis coverage

ReNeW 

Edge-SOL: S&T Issues

•  Steady-state physics affecting PMI

–  Parallel,
Perpendicular
transport
physics
 –  Recycling,
First
wall
condi7oning,
High‐T
saturated
walls
 –  Impurity
Genera7on
and
Transport
&
Radia7on
power
losses
 –  PMI
&
PFC
Matl’s
Choices
 –  Intrinsic
flow
genera7on
 –  Tri7um
&
dust
inventory
predic7on
and
control


•  Transient heat load effects

•  Core Interactions

–  Boundary
condi7on
for
Ne,
Te,
Ti,
Vplasma
profiles


–  Turbulence
spreading
into
core


ReNeW 

Edge-SOL: Challenges

•  Significant power loading, pulse length extrapolations for ITER; similar scale extrapolations from ITER to DEMO

•  Cannot simultaneously match ALL relevant dimensionless core & edge parameters in

existing experiments => validated predictive modeling essential to fill in gaps

•  Quantitative first principles predictions of all key Edge-SOL profiles, dynamics do not exist

ReNeW 

Edge-SOL: Research Program

Elements

•  Theory: Fluid & GK comparisons; RF sheath,

kinetic effects; PMI models to incorporate into

plasma simulations; self-consistent flow generation

•  Modeling: Integration of parallel & perpendicular

transport & atomic physics; integrate pedestal, SOL, and divertor simulations with PMI & PFC interactions in Steady-state & transient plasmas

•  Experiment: Existing devices: Better profile, flow &

turbulence diagnostics including better 2d/3d

coverage; RF sheath measurements, Fueling, in-situ real-time PFC, PMI measurements; Adequate run-time & data analysis coverage

ReNeW 

Energetic Particles: S&T Issues

•  Energetic ion driven instabilities

–  Stability
of
energeAc
parAcle
driven
modes
 –  Nonlinear
saturaAon,
mode‐mode
coupling
 –  Longer
Ame
scale
simulaAons
(slowing
down
Ame)
requiring
parAcle
 sources
and
sinks
 –  KineAc
effects
(moving
beyond
ideal
MHD
models
of
bulk
plasma)
 –  Impact
of
energeAc
ion
driven
instabiliAes
on
current
drive
and
bulk
 plasma
heat,
parAcle,
and
momentum
transport
 –  Effect
of
background
turbulence
on
energeAc
parAcle
driven
modes

•  Energetic ion transport and losses

–  AE
induced
transport
and
loss


–  EnergeAc
ion
interacAon
with
background
turbulence


–  Impact
of
alpha
transport
in
burning
plasma


ReNeW 

Energetic Particles: Challenges

•  Significant extrapolation in the physics of AEs to ITER (presence of many of modes, alpha

particle drive rather than beams/ICRF)

•  Linear stability predictions OK but predictive capability for nonlinear saturation and induced energetic ion transport and loss needs

development.

•  Develop appropriate models for the synthetic diagnostics in simulations for code validation against measurements of certain observable quantities.

ReNeW 

Energetic Particles: Research

Program Elements

•  Theory –  EnergeAc
ion
transport
by
AEs.

Current
models
dramaAcally
underpredict
energeAc
ion
loss
using
 experimentally
measured
mode
amplitude
and
structure
(DIII‐D
beam
ion
redistribuAon
experiments
and
 NSTX
–
TAE
induced
avalanches
are
examples).
 –  Need
to
develop
reduced
theories
to
understand/explore
this
problem.
 –  Nonlinear
saturaAon
of
AEs,
mode‐mode
coupling
 –  ConAnued
strong
role
of
analyAc
theory
in
energeAc
parAcle
physics
 –  New
methods
for
long
term
simulaAons
may
be
required
and
tested •  Modeling –  Nonlinear
MHD
codes
+
KineAcs
(e.g.
M3D
extension)
 –  EnergeAc
parAcle
transport
in
the
presence
of
mulAple
AE
modes
 –  KineAc/GyrokineAc
simulaAon
of
energeAc
parAcle
modes
 –  Comprehensive
verificaAon
of
computaAonal
models
and
soluAons
 –  Sources
and
sinks
for
long
term
simulaAon
of
the
energy
confinement
Ame
scale •  Experiment –  Expanded
energeAc
ion
distribuAon
(e.g.
FIDA)
and
loss
diagnosAcs
 –  Direct
measurements
of
energeAc‐ion
driven
modes:

enhanced
density
and
temperature
fluctuaAon
 measurements
(e.g.
reflectometry,
CECE)

 –  Development
of
local
magneAc
field
fluctuaAon
measurements
for
determining
amplitude
and
mode
 structure
 –  UAlize
basic
plasma
physics
devices



ReNeW 

Disruptions: S&T Issues

•  Disruption probability away from hard

limits

•  Detecting disruption with adequate warning

to take action

•  Developing and demonstrating workable

ReNeW 

Disruptions: Challenges

•  Can we predict operational boundaries including non-ideal (e.g. error fields) w/o empirical testing at performance limit?

•  Can we detect & avoid oncoming disruptions via real-time control?

•  Can we predict performance of mitigation schemes with sufficient confidence for e.g. DEMO licensing?

•  Can we demonstrate that mitigation scheme works as advertised?

ReNeW 

Disruptions: Research Program

Elements

•  High fidelity modeling of disruptions including whole plasma non-linear MHD, RE production & transport, mitigation scheme performance

•  Dedicated experiments on detection, avoidance and mitigation

•  Reduced modeling for incorporation into real-time control schemes

•  Key Goals: Reduce disruption probability to acceptable levels, demonstrate mitigation

ReNeW 

RF Heating & CD: S&T Issues

–  Alpha
physics
issues.
What
is
the
degree
of
LH
and
ICRF
parasiAc
absorpAon
 on
alpha
parAcles.
What
possible
transport
effects
from
RF
on
alphas
may
be
 expected
(i.e.
“alpha
channeling”)
 –  Flow
drive.
Desirable
for
suppression
of
turbulence.
Both
LH
and
ICRF
waves
 have
created
significant
toroidal
and
poloidal
flows.
The
mechanisms
are
not
 well
understood
or
predicted
by
exisAng
theory
or
models.
 –  Current
drive.
Current
profile
control
is
necessary
to
control
locaAon
of
 reversed
shear
surface
and
to
maintain
a
non‐inducAve
steady
state
plasma.
 What
are
the
power
requirements
and
degree
of
locaAon
control?
 –  Nonlinear
wave‐par7cle
interac7on.
Wave
parAcle
interacAon
has
been
dealt
 with
in
the
quasilinear
framework.
What
is
the
effect
of
nonlinear
wave‐ parAcle
interacAon
and
under
what
condiAons
are
these
effects
important?
 This
is
a
general
issue
but
for
burning
plasmas
may
be
necessary
for
accurate
 calculaAon
of
RF‐alpha
interacAons.
 –  Hea7ng.
What
are
the
power
requirements
and
coupling
efficiency
–
relevant
 for
both
LH
and
ICRF.


ReNeW 

RF Heating & CD: Challenges

•  Validity
of
geometric
opAcs
for
LHRF
in
core
 – Develop
&
Compare
against
full
wave
soluAons
 •  RF
propagaAon/absorpAon
in
edge/sol
region;
 interacAon
with
PFCs;
RF
Sheaths
&
PMI
on
 antenna
&magneAcally
connected
structures
 •  Nonlinear
wave‐parAcle
effects
on
absorpAon
 •  PredicAve
antenna
coupling
 •  RF
flow
drive:

basic
physics
not
understood


ReNeW 

RF Heating & CD: Research

Program Elements

•  Key
missing
piece:

IntegraAng
RF
w/
other
 physics
(e.g.
RF/MHD
for
predicAve
NTM
 control;
RF/turbulence
for
flow
control
&
 impurity
control)
 •  New
numerical
approaches
e.g.
for
complex
 edge
region
problems
(coupling,
RF‐PMI,
etc…)
 •  ConAnue
syntheAc
diagnosAc
development;
 new
diagnosAcs
for
edge/sol
physics
 •  Adequate
personnel
for
analysis
&
verificaAon


ReNeW 

Integrated Modeling: S&T Issues

•  Multiple time-space scales (e.g. turbulence

vs. profile evolution scales)

•  Strongly coupled phenomena challenge

traditional categorization (e.g. MHD, Turbulence, RF, etc…)

•  Integrated models require very high

reliability – failure in place brings down model

ReNeW 

Integrated Modeling: Challenges

•  Startup modeling

•  L-H and H-L transitions, ELM & sawtooth

cycles

•  Pedestal physics integrated w/ core model

•  MHD effects in steady-state

ReNeW 

Integrated Modeling: Research

Program Elements

•  Improved reduced models needed

•  Incorporate higher fidelity (“first

principles”) models into Integrated models

•  Better numerical techniques and algorithms

to span wide spatio-temporal scales

•  New frameworks (e.g. 3D for islands, ripple,

ReNeW 

Predictive HPSS Plasma Modeling

Will Require

•  New Theoretical Approaches Needed – particularly for multiple

physics and/or multiscale problems

•  Key aspect of Computational Challenges: Integration of multiple

sets of physics (e.g. RF, MHD and fast particles) into single

model

•  Some requirements for new experimental capabilities – new

diagnostics in new confinement regimes,

•  There is a role for selected dedicated subscale experiments

•  New Class of Researcher who cuts across Expts/Theory/

Modeling to rigorously validate predictive models

•  Need to develop user base for existing and emerging “first

principles” simulations & integrated modeling tools