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Supported by

Columbia UComp-X

General AtomicsINEL

Johns Hopkins ULANLLLNL

LodestarMIT

Nova PhotonicsNYU

ORNLPPPL

PSISNL

UC DavisUC Irvine

UCLAUCSD

U MarylandU New Mexico

U RochesterU Washington

U WisconsinCulham Sci Ctr

Hiroshima UHIST

Kyushu Tokai UNiigata U

Tsukuba UU TokyoIoffe Inst

TRINITIKBSI

KAISTENEA, Frascati

CEA, CadaracheIPP, Jülich

IPP, GarchingU Quebec

E.J. SynakowskiPPPL

Alcator C-Mod Ideas ForumDecember 2, 2004

The NSTX Research Program and Collaboration

Opportunities

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Theory-experiment

coupling

Experimentalcollaboration

Unique NSTX plasma properties provide scientific leverage in all major areas of toroidal confinement research

Core transport

& turbulenc

eMHD: stability & helicity injection

Wave/particle interactions

Strengthen the scientific basis for

fusion energy

Edge transport & stability

Test theory by isolating important physics and challenging models at their extremes of applicability

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Assess high low A physics with passive control

Strengthen physics basis with advanced

measurements & control at high &

low A

Optimize long-pulse, high

Strengthen physics

understanding

• Take maximal scientific advantage of ST plasma characteristics through novel diagnostics and new control tools, and targeted inter-device studies

focus for FY

‘05-‘07

NSTX research is entering a phase of advanced diagnostic implementation and advanced control

Innovative diagnostics

Control tools to test physics &

increase operating space

enablingInter-device

studies

scienceHigh impact onturbulence, waves, MHD

Unique edge B structureLarge super-

Alfvénic ni

High Vflow/VAlfvén

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• NBI + EBW CD.

• Mode control + rotation are key

• Fast ion transport & MHD important for understanding JNB

• Turbulence studies to form basis for confinement understanding

• Edge optimization & particle control required

• Successful HHFW w/ NBI ==> more JBS. Also

high value in NI-startup

40% T with ~100% INI, pulse >> skin, demands development of new tools and understanding their underlying physics

Kessel, TSCIAEA 2004

NBCD

bootstrap EBW

psi

bootstrap

NBCDEBW grad-pth

q(0)q(min)

Ongoing partnership with MIT

Common elements with error field & RWM research

Complementary *AE research with very different Vion/VAlfvén?

Build on joint edge studies, towards high k studies in the core.

Pedestal studies with very different edges. C-Mod originated Li studies at PPPL

Wave physics opportunity?

40% T , INI = 100%, pulse >> skin

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MHD & macroscopic plasma behavior

Passive stability limits & mode

characterization

C-Mod/NSTX opportunities include

• Error field studies

• Fast ion physics

• Edge stability (discussed later)

Active feedback coils

Strong shapingenabling Helicity injection

Physics of active control

Expand operating space

scienceFlows

NTM physicsNonlinear fast

ion MHDDynamo physics

Optimize stability of high

Develop startup techniques

Deepen physics understanding of

stability & reconnection

Relevant physics attributes

• Strongly driven vs. low rotation (Vflow/VA

1 on NSTX)

• Vfast ion/VA > 1 always true on NSTX.

• Different means of generating fast ions

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Rotation effects are strong in NSTX plasmas

W. Park, J. Menard

Rotational shear also strong candidate for internal mode saturation

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Differences & similarities in plasma parameters may allow comparative studies in mode control & mode locking

• Compared to C-Mod,

– ~ similar sound speed, C-Mod has smaller VAlfvén. NSTX has Larger Vflow/Valfvén.

Implications for mode damping/locking?

– At lower A, higher n modes expected to be more important --> benchmark RWM theories

• Likely source of complementarity: error field and mode locking studies

Columbia U.

Feedback coils

Contact jmenard@pppl.gov, ssabbagh@pppl.gov.RWM: camera image & DCON code

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NSTX’s large population of super-Alfvénic fast particles enables an important branch of nonlinear

MHD physics to be studied• Vfast ion/VAlfvén ~ 3, similar to ITER

values of ~ 2.

• Access to multimode Alfvénic turbulence in nearly every NBI discharge on NSTX

• MSE commissioned, with goal of routine EFIT constraints next run

• Features for scientific leverage between C-Mod & NSTX include– similar shape, different R/a– Different driving mechanisms

Already joint XPs with DIII-D. Contact efredrickson@pppl.gov

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Transport & turbulence (core)

Global scalings

Local

Edge turbulence

Confinement optimization

Role of + Er in & turbulence

Optimize confinement +

JBS in long-pulse, high

Extend physics understanding of turbulence

to unity

NSTX transport physics

• Role of : onset of electromagnetic effects broadens theory/experiment comparisons

• Electron transport: Broad range of k for theory tests

enablingParticle control: lithium

q profile & reverse shear

scienceElectron thermal transport: High k

scattering

Ion, electron transport: low k

imaging

e-m effects, low & hi k

C-Mod/NSTX research opportunities

• High k comparisons at low & high and the onset of e-m effects

• Core ITBs with RF

• Dimensionless similarity?

NB vs HHFW heating

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Understanding electron thermal transport will be a focus for ‘05 - ‘07

• The dominant energy loss channel & a topic of broad importance to fusion & burning plasmas, including ITER.

• Potentially important for RF & CD

• While e transport is rapid, it can be modified– Why the flat center?

• Collaborative core transport similarity experiments through ITPA (MAST, DIII-D)

Faster Ip ramp

Te

ch

ang

e (%

)

t (ms)

137.5 cm

134 cm

131 cm

127 cm

R0=101 cm

Stutman, JHU

LeBlanc, R. Bell, Kaye

Rapid cold pulse propagation following ELM

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High k scattering measurements will be developed in FY’ 05

• Initial system will allow range of k measurements in select locations (2 - 20 cm-1) with good spatial resolution & ∆n/n < 0.01%

• Major installation this opening.

High k scattering

Luhmann (UC Davis), Munsat (U. Colorado) Mazzucato, Park, Smith (Princeton U.)

1.0 10k (cm-1)

Contact hpark@pppl.gov

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Waves & energetic particles

HHFW heating, phasing, & CD

EBW emissions

Coupling startup techniques to ramp-up

Wave physics in overdense plasmas

Reduce V-s through JBS

and direct CD

Extend physics understanding

of waves in overdense plasmas

NSTX wave-particle physics

• HHFW, EBW: wave coupling, propagation & deposition for overdense plasmas (for ST, RFP)

• EBW: Ohkawa current drive with high trapping fraction

scienceHHFW wave physics from

antenna to core

EBW physics: mode conversion & f(v)

modification

Super-Alfvénic particles &

MHD

enabling

EBW tube. Launcher

development

Heat low Ip plasmas for

ramp-up

NBI at modest B

Opportunities with MIT/ C-Mod program

• Strong RF theory & modeling effort at present, including ongoing EBW theory research

• Direct measures of fast wave deposition

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HHFW Absorption Depends on Antenna PhasingHHFW modulated to assess % absorption

k||=14 m-3 80% 7 m-1 (ctr) 75% -7 m-1 (co) 40% 3 m-1 10%

Edge ion heating, parametric decay of HHFW

Evidence for parametric absorption processes found in spectroscopy, RF probes

Absorption

Hot component

Cold component

Biewer, APS invited 2004

Contact jrwilson@pppl.govckphillips@pppl.gov

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Can overdense C-Mod plasmas be created so that fast waves can be launched and

diagnosed?

• Need for NSTX: validate fast wave physics– Core deposition to be sampled with modified edge

reflectometer (ORNL) up to ne = 6x1012 cm-3

• Opportunity for C-Mod program: Clarify & test FW deposition theory with PCI deeper into the core– Perhaps 80 MHz, high density operation will yield

an appropriate overdense condition for the RF?

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ST properties and recent experiments make EBW attractive & high priority

• Ongoing research effort with MIT theory

• EBW current drive takes advantage of high ST electron trapping fraction via Ohkawa effect. The ST is perfect for exploring this science.

• Recent NSTX emissions evaluating EBW coupling are promising

• Modeling indicates efficient off-axis current drive

Compx Genray/CQL3D

Contact gtaylor@pppl.gov

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C-Mod/NSTX opportunities

• Different edge Bp/B T

• Different values of B, ne, Te…

Plasma boundary interfaces

Power balance

Heat flux scaling

Pedestal & ELM character

Lithium pellets & coatings

Fueling studies

SOL transport

Optimize high , long pulse

regimes through pedestal

modification

Assess boundary

control needs for steps

beyond NSTX

Boundary physics opportunities

• Advanced heat and particle flux management techniques relevant to all toroidal confinement concepts

• SOL transport: intermittency & shear Alfvénic turbulence

Lithium studies for influx control

Optimize ELMs

Radiative divertor regimesenabling

Pedestal-core connection

Pedestal stability at low A

SOL transport & turbulence

science L-H transition physics

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Improved diagnostics are allowing details of ELM characteristics to emerge

• Diagnostics (e.g. fast camera) now allow detailed documentation of ELM dynamics, tests of theory

• On NSTX, Type V ELMs: small, with little change in stored energy– So far, found in high

ne regimes– Possible platform for

comparitive study with benign regimes on C-Mod

Type V Type I

Small, filamentary, perturbation

Larger low n perturbation

Contact rmaingi@pppl.govktritz@pppl.gov

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NSTX capability for pedestal studies will be improved in ‘05

• MPTS: additional channels added in edge and core.

• CHERS: resolution surpasses carbon ion gyroradius at the edge

• Edge reflectometry for ne

Contact: rmaingi@pppl.gov

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Imaging & probe measurements provide a powerful test bed for edge turbulence codes

• Already a strong collaborative effort with the C-Mod program

• L-H transition physics, turbulence structure and dynamics are all possibilities

• NSTX may be revealing new class of turbulence not seen in DIII-D or C-Mod– BOUT simulations point to “electrostatic

shear Alfvén eigenmodes” (Umansky, LLNL).

• Can we better understand the limits of edge codes through this sort of comparative study?

L mode

BOUT simulations underway based on measured profiles & NSTX geometry (preliminary)

Umansky, LLNL

Zweben

Probes: Boedo

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Lithium edge flux control studies start with pellets, and may culminate in a powerful edge control approach

• Li coatings: localized, 1000 Å before every shot

e-beam for Li coatings in ‘06

Liquid lithium module: decision following coatings studies

• Under ALIST group of VLT• Would represent a revolutionary

solution for both power and particle handling

Li pellets: injector commissioned in ‘04

• Develop deposition techniques in ‘05

Contact hkugel@pppl.gov, rkaita@pppl.govboedo@fusion.gat.com

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NSTX research run plan extends to 18 run weeks

• Scheduled to start in late winter

• Contacts: myself, Jon Menard (this run’s run coordinator), ET leaders, Stan Kaye, Mike Bell– MHD: Steve Sabbagh, Dave Gates– Transport: Stan Kaye, Dan Stutman– Boundary: Bob Kaita, Jose Boedo– HHFW/EBW: Cynthia Phillips, Randy Wilson– Integrated scenarios: Rajesh Maingi, Chuck

Kessel

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There are many opportunities for additional, high leverage collaborative research

• A key aspect of our research approach is to use similarities & differences between different devices to challenge theories & models at their extremes

• Scientific progress is colinear with demonstrations of advanced scenarios

• Improved diagnostics and control capability will enable more sophisticated comparative studies this run

• We welcome this as part of a continuing constructive dialogue between the two programs

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FESAC Theme: Understand & control the processes that govern confinement of heat, momentum, and particles

FESAC Theme: Learn to use energetic particles & e-m waves to

sustain and control high temperature plasmas

FESAC Theme: Understand the role of magnetic structure on confinement, & plasma pressure limits

Microscopic ion, electron, and tearing turbulence measurement & theory comparison over wide range in , flows, and magnetic shear, with good average curvature and high trapping

Stability pressure limits & magnetic reconnection vs. A, shape, profile, q & flows, for internal & external modes with Vflow/VA < 0.4 & unity ; helicity transport

EM waves in overdense plasma; Phase space manipulation with high electron trapping; energetic ions with large orbits; Alfven eigenmodes and turbulence with Vfast/VA >> 1

FESAC Theme: Learn to control the interface

between a 100 million degree plasma and its

room temperature surroundings

Physics of ELMs, pedestal, SOL turbulence & high

divertor heat flux, with large in/out asymmetry; Li

coatings & liquid surface interactions with plasma.

NSTX research for ‘05 - ‘07 is well aligned with the fusion program’s scientific priorities and supports strategic goals

NSTX

_

Demonstrate Feasibility with Burning Plasmas

Develop Understanding and Predicitve Capability

Determine Most Promising Configurations

Develop New Materials, Components, & Technologies

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Plasma flows will be a focal point of research through ‘07

• Understanding momentum transport a national transport priority

• Motivated by observations– Counter-directed flow with co-

injection – V, V with HHFW & prior to

ohmic H modes

• Needed to reconstruct Er & profile

• V measurements deeper in the core will be developed for ‘06

R. Bell

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NSTX research led to an expansion of operating space in 2004

Reduced latency improved vertical control at high-, high-T

Capability for higher allowed higher IP/aBT

Significantly more high-T

(N=6.8 %mT/MA achieved)

More routine high Longer current flattop duration pulse = (>0.85 Ip,max)

Time of peak T