Multi-Scale Transport and Turbulence Physics in NSTX

Stanley M. KayeFor the NSTX Team

Tokamak Planning WorkshopPSFC, MIT

Sept 17, 2007

Supported byOffice ofScience

Culham Sci CtrU St. Andrews

York UChubu UFukui U

Hiroshima UHyogo UKyoto U

Kyushu UKyushu Tokai U

NIFSNiigata UU Tokyo

JAERIHebrew UIoffe Inst

RRC Kurchatov InstTRINITI

KBSIKAIST

ENEA, FrascatiCEA, Cadarache

IPP, JülichIPP, Garching

ASCR, Czech RepU Quebec

College W&MColorado Sch MinesColumbia UComp-XGeneral AtomicsINELJohns Hopkins ULANLLLNLLodestarMITNova PhotonicsNew York UOld Dominion UORNLPPPLPSIPrinceton USNLThink Tank, Inc.UC DavisUC IrvineUCLAUCSDU ColoradoU MarylandU RochesterU WashingtonU Wisconsin

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NSTX Can Address T&T Issues Critical to Both Basic Toroidal Confinement and Future Devices

• Critical issues for future (including Burning Plasma) Devices (ST-PE, CTF; ITER)– Confinement enhancement (H-factor) at low & high Pheat/PLH

– Hot-ion H-mode operation - neoclassical ion transport– Maximize neutron production &/or fusion gain – optimize electron

transport– Predictive understanding necessary

• NSTX can address these issues– Dominant electron heating with NBI: relevant to -heating in ITER– Strong rotational shear that can influence transport– Anomalous electron transport can be isolated: ions close to

neoclassical

– Large range of T spanning e-s to e-m turbulence regimes

– Localized electron-scale turbulence measurable (e~0.1 mm)

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Transport and Turbulence Studies Take On a Multi-Faceted Approach

Transport coupled to turbulence measurements over a wide k-range

Experiment coupled to gyro-kinetic theory/simulation results - GTC-NEO, GS2, GYRO, GTC, GEM - pTRANSP

Verification and validation of theory and models at all levels - Synthetic diagnostics in gyro-kinetic codes - Fluctuation spectra, mode structure - Transport fluxes, ’s, D’s

Ultimate goal: Comprehensive Understanding Predictive Tool

ETGITG/TEM

TEARINGKBM

0.1 1 10 100k(cm-1)

wave ScatteringLow-k

wave Imaging

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Global Confinement Research Has Established Scaling Trends wrt Dimensional and Dimensionless Variables

4 MW

4 MW(Kaye et al, PRL 46 [2006] 848)

-scaling high priority ITPA topic: Shape (ELMs) matter!

Parametric dependences differ from those at higher R/a

=2.1 =0.6 =1.85 =0.6

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Global Confinement Studies are Important for Being Able to Predict the Performance of Future Devices

• 2009-2010– Source of variation in -degradation of confinement important

for ITER• ELMS vs shape (are the two coupled)?

– Dependence of E on R/a for optimizing ST-PE, CTF designs

• Within NSTX (limited range accessible: 1.3 to 1.6)• Complete NSTX/DIII-D similarity experiment

• 2010-2013– Verify scaling trends at high Pheat/PLH to support ST-PE, CTF

physics designs• Second beam line (+ 6 MW)

Most global confinement studies have given way to local transport studies, but some important research opportunities remain

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Ion Transport Found to Be Near Neoclassical In H-modes

Neoclassical levels determined from GTC-Neo: includes finite banana width effects (non-local)

Controls E scaling with Ip

Neoclassical

Neoclassical orbit squeezing/shrinkingmay be responsible for setting i-scalelimit of Ti gradient

Linear GS2 calculations indicatesuppression of low-k turbulence by ExB shear during H-phase (GTC non-linear also)

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Goal of Ion Transport Studies is to Establish a Predictive Understanding of Transition Between Neoclassical and

Turbulent Transport Regimes

• 2009-2010– Actively change ITG/TEM driving/damping terms (Te/Ti, ExB

shear)• HHFW → NBI, Non-Axisymmetric Magnetic Perturbations

(NAMP) braking– nRMP to slow plasma, reduce ExB to point where ion transport

becomes anomalous

– Relation of first low-k turbulence measurements to transport• Low-k fluctuation diagnostic• Full FIDA, neutron collimators for Pheat

– Role of Zonal Flows in edge• Doppler reflectometry, ERD upgrade

– Ion internal transport barrier studies• Relation to current profile, integer q, Zonal Flows• Validation of neoclassical orbit shrinking theory

- Predictive understanding crucial for design/operation of ST-CTF (neoclassical ions)- NSTX tools allow for transitioning between turbulent and neoclassical transport

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Ion Transport Research in Latter Part of Five Year Plan Will Allow Us to Draw Definitive Conclusions Concerning

Neoclassical vs Turbulent Transport

• 2011-2013– More detailed comparison of inferred i and low-k fluctuations to

gyro-kinetic predictions• Comprehensive validation of neoclassical and ITG theories

– Synthetic diagnostics built into G-K codes

• Assessment of non-local transport due to large

• Zonal Flow dynamics in edge and core (test theoretical q-dependence)

– Assessment of ion transport and turbulence levels at high Pheat/PLH at various ExB for establishing physics basis for ST-PE, CTF

• Second beamline• Internal coils for NAMP braking

– Neoclassical theory development with full FLR

• 2013– Low-to-medium k turbulence levels measured with Microwave

Imaging Reflectometer– Ion transport in OH, RF plasmas with Ti/Te<1

• Imaging X-ray crystal spectrometer (non-beam based)

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NSTX Is In a Strong Position to Study and Understand Electron Transport

Electron transport anomalous: controls BT scaling

Consistent with high-k fluctuations

Low-k microtearing important in “Hybrid” and weak RS discharges

High-k (ETG?) fluctuations seen to increase with increasing R/LTe

14 cm-1

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A Predictive Understanding of Electron Transport is Critical to Optimizing Fusion Gain/Neutron Production for BP Devices

• 2009-2010– ID of TEM/ITG using present high-k system

• Collisionality scans• Establish critical gradient using HHFW to change R/LTe

• Connect to inferred transport levels– Full FIDA, neutron collimators for Pheat(r)

– Role of RS, low order rational q for eITB formation– Microtearing mode ID

• Change driving/damping(?) terms: ExB shear• Initial internal B measurements with MSE

– Perturbative electron transport using ELMs and pellets• High resolution edge SXR• Relation to high-k turbulence

Compare measurements to results of gyrokinetic calcs with built in synthetic diagnostics for V & V

- Electron transport is one of the top research priorities- Anomalous electron transport can be “isolated” (i.e., ion transport neoclassical)

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Electron Transport is One of the Top Research Priorities

• 2010 - 2011– Local modification of electron transport and turbulence

• Low power EBW (200 kW)• Modify q-profile to induce electron ITB• Assess turbulence spreading with low and high-k fluctuation measurements

– Modulated EBW to probe local critical gradient physics• High-resolution Tangential Optical SXR (TOSXR)• Relation to changes in high-k turbulence

– Microtearing mode ID continued• Internal B, low-k for mode structure

– Verify transport trends at high Pheat/PLH

• Second beamline

• 2012 – 2013– Detailed medium-to-high k turbulence with kr & k

• Microwave scattering high-k upgrade• Microwave Imaging Reflectometer• Mode structures, full frequency spectra, dispersion characteristics• Radial streamer ID

– Localized heating to probe critical gradient physics, turbulence spreading• High power EBW (2 MW)

Full V & V critical to effort

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Momentum Transport Studies Will Address Source of High-Rotation and Relation to Energy Transport

i, scaling different at low R/aPerturbed momentum transport studies using nRMP (n=3) braking and spin-up indicates significant inward pinch velocity

Due to ITG suppression?

Is neoclassical?

Peeters et al

Fit with finite v,pinch

Fit with v,pinch=0

TRANSP

• 2009 – 2010 - Validation of neoclassical theory (poloidal CHERS for v) - Determine vpinch, under a variety of conditions

- NAMP for magnetic braking

- Tests of inward pinch theories - Test of NTV theory for magnetic braking - Comparison with initial low-k• 2011-2013 - Relation of vpinch, to low-k in both L and H - Zonal flows/GAMs and relation to other microinstabilities - Further vpinch, assessment (internal NAMP coils for magnetic braking)• 2013 - Intrinsic rotation studies with Imaging X-ray Crystal Spectrometer

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Particle Transport Studies Important for Establishing Regimes of Turbulent vs Neoclassical Transport

Impurity injection experiments/theoretical modeling indicateneoclassical level transport for injected Neon in H-mode - Consistent with neoclassical ion energy transport

• 2009 - 2011 - D & particle transport in core (NBI-fueling dominated) - NUBEAM for S(r) - Relation to thermal , transport, core turbulence (low-k) - Density peaking - Modulated core fueling with beam blips; determination of Dpert, vpinch

- D & particle transport in outer region - S(r) from extended modeling (DEGAS2/UEDGE) - Relation to edge turbulence (Boundary) - Impurity transport using gas puffing, TESPEL, high res SXR to deduce Dpert, vpinch

- Helium transport studies (He puffing or He discharges)

• 2011 – 2013 - Determine role of low-k turbulence in controlling particle transport - Modulated particle transport studies continue with second beamline

Effect of Lithium conditioning

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Theory Tool Development

• 2D/3D state-of-art neutrals package for transport studies (TRANSP)• Full FLR effects for complete non-local neoclassical transport• Gyro-kinetic codes

– GS2 (flux tube)

– GYRO

– GTC (kinetic electrons, finite-, multi-ion species)

– GEM (low-k microtearing, kinetic electrons for ETG)

– Synthetic diagnostics for V & V

– High + Low k non-linear calculations numerically expensive: is scale-separation possible when ITG suppressed, or is turbulence spreading important?

• Predictive tools– pTRANSP for scenario development

– Low R/a relevant transport model (TGLF?)

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Proposed Five-Year Research Plan (2009-2013)