DIII-D Research Advancing the Scientific
Basis for Burning Plasmas and Fusion EnergybyW.M. Solomon

for the DIII-D Team

Presented at the26th IAEA Fusion Energy Conference
Kyoto, JapanOctober 17-22, 2016
This work was supported by the US Department of Energy under DE-FC02-04ER54698.
DIII-D data shown in this paper can be obtained in digital format by following the links
at https://fusion.gat.com/global/D3D_DMP.

0

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rsDIII-D Advances Fusion Energy Development ByFocusing on Four Research Elements
DIII-D Research ElementsITER

Control Transient Behavior

Develop Relevant Boundary Solutions
PlasmaExhaustStrengthen the Basis of Fusion ScienceDetermine Path to Steady-State

1

DEMO

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

DIII-D Advances Fusion Energy Development By
Focusing on Four Research Elements
DIII-D Research Elements

Control Transient Behavior• Disruption mitigation• Low torque stability• ELM control

ITER

Develop Relevant Boundary Solutions

PlasmaExhaustStrengthen the Basis of Fusion ScienceDetermine Path to Steady-State

2

DEMO

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

DIII-D Is Uniquely Equipped with Primary Disruption
Mitigator for ITER: Shattered Pellet Injection (SPI)• Large cryogenic pellet shattered in guidetube provides pulse of tiny solid shards• Varying deuterium / neon mix provides
control of disruption characteristics• Achieved first demonstration of runaway
electron plateau dissipation with SPI
Increases confidence that SPI will be aneffective disruption mitigation tool for ITER

3W.M. Solomon / IAEA16 / October 2016

Shiraki – EX/P3-20
Commaux – EX/9-2
072-1/WMS/rs

Gamma Ray Spectroscopy Reveals Growth of High Energy
Runaway Electrons (REs) Matches Theory• High energy REs grow withelectric fields E/Ecrit~2– Theory predicts growth at
E/Ecrit~1.6• Lower energy RE growth athigher E/Ecrit~5– Similar to previous HXR
measurements

More destructive high energy REs
are more difficult to dissipate
à better to prevent initial growth
4W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

MHD Spectroscopy Used to Identify the Approach toInstability in Low Torque ITER Baseline• ITER baseline typicallycharacterized by 2/1 tearing
modes that lock at low torquePlasma response amplitude (G/kA)
108• Plasma response amplitude
6increases as rotation is reduced
4255

10152025Rotation at ρ~0.7 (krad/s)

W.M. Solomon / IAEA16 / October 201630

Turco – EXP/3-14072-1/WMS/rs

MHD Spectroscopy Used to Identify the Approach toInstability in Low Torque ITER Baseline• ITER baseline typicallycharacterized by 2/1 tearing
modes that lock at low torque• Plasma response amplitude
increases as rotation is reduced• Onset of 2/1 instability precededby increase in plasma response
Potential to use real-time measured change in plasma
response as part of disruption warning system
6W.M. Solomon / IAEA16 / October 2016

Turco – EXP/3-14072-1/WMS/rsdata8trendline• Control of applied mode
spectrum important tooptimize response for
ELM suppression

HFS Response (G)• HFS response measurement
strongest at low collisionality

LFS Response (G)ELM Suppression in ITER Baseline Associated νwithLow
e*= 0.3, 4Collisionality Edge Mode on High6Field Side (HFS)
42ne scan

0

2.0
1.5

ELMsuppression@ low ννe*

1.0
0.5
0.0090180270360

Δφ UL
applied n=2spectrum (ΔϕUL)

Importance of enhanced response at low
collisionality confirmed by ELM suppression
on ASDEX-Upgrade à favorable for ITER
7W.M. Solomon / IAEA16 / October 2016

Paz-Soldan – EX/1-2
Nazikian -072-1/WMS/rsPD

Discovered Stationary Quiescent H-mode Plasmas with Zero
Net NBI Torque and High Energy Confinement• New state with increased pedestal height, width and confinement• Bifurcation to new regime triggered using torque ramp down
• Associated with changes in ExB shear and increased edge fluctuations
After transition •Standard QH
H98~1

Wide pedestal withedge fluctuations
H98>1.3, bN>1.8

Beforetransition towide pedestal
0.85

0.90
r0.95

1.00

Exciting potential solution to high performance low torque ELM control

8W.M. Solomon / IAEA16 / October 2016

Chen – EX/3-2
072-1/WMS/rs

DIII-D Advances Fusion Energy Development By
Focusing on Four Research Elements
DIII-D Research Elements

Control Transient Behavior

ITER

Develop Relevant Boundary Solutions• Divertor drifts• Radiation shortfall• 3D divertor heat fluxesPlasmaExhaustStrengthen the Basis of Fusion ScienceDetermine Path to Steady-State

9DEMO

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

Drifts Affect Divertor Asymmetries andDetachment Threshold• Inner divertor exhibits higher ne and lower Te for normal BT direction

2D Divertor
Thomson
Scattering (DTS)10

W.M. Solomon / IAEA16 / October 2016

McLean – EX/2-1
072-1/WMS/rs

Drifts Affect Divertor Asymmetries andDetachment Threshold• Inner divertor exhibits higher ne and lower Te for normal BT direction– Reversing BT mitigates in-out asymmetry

2D Divertor
Thomson
Scattering (DTS)

11W.M. Solomon / IAEA16 / October 2016

McLean – EX/2-1
072-1/WMS/rs

Drifts Affect Divertor Asymmetries andDetachment Threshold• Inner divertor exhibits higher ne and lower Te for normal BT direction– Reversing BT mitigates in-out asymmetry• Reverse BT lowers density
for detachment in H-mode• Effects understood due tointerplay between radial andpoloidal ExB drifts– Reproduced qualitatively in UEDGE simulations with full cross-field drifts

Future divertor designs can be better optimized byaccounting for asymmetries due to drifts
12

W.M. Solomon / IAEA16 / October 2016

McLean – EX/2-1
072-1/WMS/rs

Radiation “Shortfall” Caused by Under-Prediction of theDivertor Density and Uncertain Atomic Physics• SOLPS and UEDGE modeling of D+C
plasmas show significant “shortfall” inradiated power

13

W.M. Solomon / IAEA16 / October 2016

McLean – EX/2-1
072-1/WMS/rs

Radiation “Shortfall” Caused by Under-Prediction of theDivertor Density and Uncertain Atomic Physics• SOLPS and UEDGE modeling of D+Cplasmas show significant “shortfall” inradiated power• Shortfall can be reduced by matching
the X-point density measured by DTS– Usual approach matches upstream density

14W.M. Solomon / IAEA16 / October 2016

McLean – EX/2-1
072-1/WMS/rs

Radiation “Shortfall” Caused by Under-Prediction of theDivertor Density and Uncertain Atomic Physics• SOLPS and UEDGE modeling of D+C
plasmas show significant “shortfall” inradiated power• Shortfall can be reduced by matching
the X-point density measured by DTS– Usual approach matches upstream density• Shortfall eliminated in helium plasmas– No uncertainties in hydrocarbon reactions

Highlights need to improve D atomic andmolecular physics and parallel transportmodel in the divertor

15W.M. Solomon / IAEA16 / October 2016

McLean – EX/2-1
072-1/WMS/rs

Spatial Extent of Divertor Electron Temperature Lobes Due toRMP Are Reduced at High Density• At moderate density, lobes in Te
extend to the divertor plates, heat
flux profile also shows 3D structure#164721#167422• At higher core densities these lobes
shrink and move away from target– Before partial detachment andcontinuing through to detachment#164725– May be sensitive to poloidal
spectrum and plasma response

Partial detachment of divertor may besufficient to eliminate non-axisymmetricheat flux striations in ITER
Briesemeister – EX/7-3Rb
Lore - TH/P6-12
16

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs-0.5

Experiments with Tungsten Rings Reveals Metal
Influx Is Predominantly from Strike Point Location
Two rings of W Tiles-1.0• Different W isotopes isolate
strikepoint from divertor shelf

Shelf:
Enriched W182
-1.5

17Strikepoint:
Natural W
1.0

W.M. Solomon / IAEA16 / October 2016

1.2

1.4

1.6

1.8

2.0

Unterberg - PD
072-1/WMS/rs
Ding – MPT/1-2RB

2

-0.5

Experiments with Tungsten Rings Reveals Metal
Influx Is Predominantly from Strike Point Location
Two rings of W Tiles-1.0
44• Different W isotopes isolate
strikepoint from divertor shelf

2

10

Floor/Shelf
Floor/Shelf
2RatioRatio
Shelf:

10Enriched W182
8866Strikepoint:
4NaturalW

42

1.0

1.2
1W Areal Density [x10 W-m ]18

W.M. Solomon / IAEA16 / October 2016

1.82.020.4

Midplane

0.2Strike W Floodominates-20.4

180.2

Floor Density

Shelf Density

0.0

1.6

118

Suggests control ofstrikepoint flux is key tolimiting core contamination

21.4-2-1.5

W Areal Density [x10 W-m ]• Little contribution of W182 fromshelf tile in high power H-mode

020.04 06

Shelf Density

2 8 410 612 814 1016 12
R -RSEP [cm]R -RSEP [cm]

Unterberg - PD
072-1/WMS/rs
Ding – MPT/1-2RBDIII-D Advances Fusion Energy Development By
Focusing on Four Research Elements
DIII-D Research Elements

Control Transient Behavior

ITER

Develop Relevant Boundary Solutions

Strengthen the Basis of Fusion Science••••

Intrinsic rotation drive
Particle transport
Stiffness
LH physics

Determine Path to Steady-State

19PlasmaExhaustDEMO

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

r* Scaling of Intrinsic Drive Projects to a Torque Comparable tothat from Neutral Beams on ITER
• Experimental scaling determined • Simulations with GTS gyro-kinetic
code reproduces reversal ofin joint study with JET
core intrinsic rotation– Favorable scaling still leads torelatively low level of rotation

Norm. Intrinsic
Torque

ITER

1.0

0.1
0.001

ITER
Intrinsic torque>30 Nm
NBI torque ~ 30 Nm

Grierson – EX/11-1
Wang - TH-C/P3-12
deGrassie – EX/P3-13

20

ρ*DIII-D
JET

DIII-D

0.010

Although intrinsic rotation projected to
be low, profile effects may still lead to
improved performance
W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

Increase in Density Profile Peaking at Low Collisionality
Appears Due to Changes in Beam Fueling• Increase density peaking
observed in dimensionlesscollisionality scaling experiment

21W.M. Solomon / IAEA16 / October 2016

Mordijck – EX/P3-9072-1/WMS/rs

Increase in Density Profile Peaking at Low Collisionality
Appears Due to Changes in Beam Fueling• Increase density peaking
observed in dimensionlesscollisionality scaling experiment• Change in peaking is reproducedby changes in core fueling only– Assuming no change innormalized transport from highcollisionality case

Database scalings may be
too optimistic for densitypeaking in ITER
22

W.M. Solomon / IAEA16 / October 2016

Mordijck – EX/P3-9072-1/WMS/rs

Ion Stiffness Does Not Clamp Ion Temperature
Gradient in Power Scans• Stiffness paradigm is large
incremental transport above
critical gradient

23

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

Ion Stiffness Does Not Clamp Ion Temperature
Gradient in Power Scans• Stiffness paradigm is large
incremental transport above
critical gradient• Ion thermal diffusivity drops withincreasing power

24

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rsIon Stiffness Does Not Clamp Ion Temperature
Gradient in Power Scans• Stiffness paradigm is large
incremental transport above
critical gradient• Ion thermal diffusivity drops withincreasing power• Stiffness not observed becausetemperature is not kept constantSuggests fusion gain will
increase with heating morethan stiffness would imply
25

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

Theory-Experiment Validation Has Increased
Confidence in ITER Achieving its Q=10 mission• Self-consistent coupling of core &pedestal theoretical models– No free or fit parameters• Whole profile iteration converges
to unique solution(TGLF+NEO)– Predicts βN to ~15% in
200 DIII-D cases• Enables prediction andoptimization of ITER fusion gain:
Q~12 possible

Self consistentsolution

New frontier: Multi-scale turbulencesimulations and TGLF improvement
Meneghini – TH/9-1
Holland– TH/6-1
Staebler – TH/P2-826

Initial guess

W.M. Solomon / IAEA16 / October 2016

Self-consistent iteration
072-1/WMS/rs

Dual Mode Nature of Edge Turbulence May Explain
Isotope and Density Scaling of L-H Power (d)Threshold• Counter-propagating turbulence modes
appear to interact to increase turbulent
Reynolds stress driven phase velocity shear(er~0.96

Ion• Increased shear facilitates L-H transitionmod

ne~1.5x1019m-3(d)(e)IonmodIoe

Elec trm o d one

Minimum inLH power
thresholdcorrelatedwith dualmodes

en

Yan – EX/5-1
Schmitz – EX/P3-1127mode
19 -3
ne~1.5x10 m
W.M. Solomon / IAEA16 / October 2016

ne~4.2x1019m-3072-1/WMS/rs

DIII-D Advances Fusion Energy Development By
Focusing on Four Research Elements
DIII-D Research Elements

Control Transient Behavior

ITER

Develop Relevant Boundary Solutions
PlasmaExhaustStrengthen the Basis of Fusion ScienceDetermine Path to Steady-State• Shafranov shift stabilization• Fast ion transport• Core-edge integration
28

W.M. Solomon / IAEA16 / October 2016

DEMO072-1/WMS/rs

Excellent Confinement in High bP Scenario Is Due toShafranov Shift Stabilization• Large radius ITB and excellent
confinement maintained at
reduced rotation or q95

High H at lower rotation

High H at lower q95• ITB lost when Shafranov shift(∝bP) gets too lowProjects to ITER Q=5 at q95~6
if high confinement
maintained with high q0 (NCS)

29

Qian – EX/4-2

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

Incorporating Negative Central Shear Mitigates
Confinement Degradation with Increasing Te/Ti
Increase Te/Ti with ECH

ci {w/ ECH} / ci {w/o ECH}ci {High Te/Ti}
ci {Low Te/Ti}• Plasmas with standard positive
shear (PS) show reduced Ti
when ECH power addedΣñ {High Te/Ti}Σñ {Low Te/Ti}• Increase in Te/Ti has less impact
on fluctuation levels withnegative central shear (NCS)

Advanced scenarios canmaintain performance in burning
plasma relevant conditions

30

W.M. Solomon / IAEA16 / October 2016

PSNCS

ñ {w/ ECH} / ñ {w/o ECH}
PSqminNCS

Yoshida – EX/8-1
072-1/WMS/rs

Fast Ion Transport Exhibits a Critical-Gradient LikeBehavior Driven by Overlap of Multiple Unstable Modes• Rapid increase in fast ion flux
above threshold in beam power

ORBIT CODE
matches data

Fastlosses
Fast ionIon LossPDF(counts)# Events104• Intermittent bursts of losses
observed above thresholdt=516-948 ms
103

Increasingpower

102
101
1.0

1.5

2.0

Raw/Smoothed
Data (V/<V>)
Fluctuation amplitude
31

W.M. Solomon / IAEA16 / October 2016

Collins – EX/6-2072-1/WMS/rs2.5

Large Impact of ECH on Alfvén Eigenmode (AE) Activity inDIII-D Plasmas Explained by Finite Temperature Effects
ECH modification of RSAEs in DIII-D• ECH drastically alters AE activity– Reverse Shear AE (RSAEs)
particularly sensitive

fTAE
fRSAE-min• RSAEs exist between a minimum
frequency and the TAE frequency– Temperature gradient andelongation modify minimum
frequency

fTAE
fRSAE-minSuggests tailoring oftemperature profile can control
RSAE-driven transport32• Including these effects
correctly predicts existence
and evolution of RSAEs

W.M. Solomon / IAEA16 / October 2016

Van Zeeland – EX/P3-24
072-1/WMS/rs

ELM Suppression Achieved in ≈1 MA Fully Non-Inductive
Hybrid with Minimal Impact on Performance• High bN + bootstrap, and coupling
to weakly stable edge kink mode
gives stronger response than inITER baseline– Wider q95 range (6-7.5)
for suppression– ~5% reduction in H98• Separately, “puff-and-pump”
radiative divertor halved
peak divertor heat flux
– Again little change inconfinement (~10%)

ECCD

0.8

NBCD

0.4
0.0
0.2 Vsurf(V)0.0-0.2
432
104 D
3 a2
100

bootstrapbN
IRMP (kA)qmin

1

ELM control appears morerobust in steady-state scenarios
33161403

1.2 IP (MA)W.M. Solomon / IAEA16 / October 2016

234Time (s)56Petty – EX/4-1
072-1/WMS/rs
Petrie – EX/P3-27

Future DIII-D Enhancements Provide Flexibility toContinue to Address these Key Issues
DIII-D Research Elements

Enabled by DIII-D Enhancements
Improved 3D control

Control Transient
Behavior

Increased electron
Heating/current drive

2nd SPI

Lower divertor
bolometer upgrade

Divertor closure
modifications

Develop Relevant
Boundary Solutions
Strengthen the Basis ofFusion Science

PEP- II Linac Accelerator Systems Department

B-Factory RF Klystrons (1.2 MW•

Improved diagnostics

Determine Path toSteady-State

Increased co-current,
off-axis current drive“Helicon” system

C. Pearson

34

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

DIII-D Has Advanced the Scientific Basis for Fusion Energy:
Preparing for ITER and Laying the Foundation for Steady-State• Increased confidence in our ability to handle and control transients(disruption mitigation, ELM suppression, QH-mode)• Improved understanding of processes relevant to divertor dynamics(drifts, radiation shortfall)• Key advances in understanding in momentum, particle andthermal transport• Extended steady-state scenarios to more reactor relevant regimes(rotation, Te/Ti) and integrated boundary physics solutions(ELM-suppression and radiative divertor)

35

W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs

Disclaimer
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither theUnited States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, orassumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus,product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to anyspecific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does notnecessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or anyagency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the UnitedStates Government or any agency thereof.

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W.M. Solomon / IAEA16 / October 2016072-1/WMS/rs