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N S T X-U

N S T X-U. Supported b y. Pr og ress a n d P l a n s f o r Pe d esta l Ph ys i cs a n d C on tr o l Ahme d Diallo R . Maingi , S. P . G erhard t, J-W Ahn. C oll o f W m & Mary Columbi a U CompX Genera l A to m i cs FIU INL Johns Hopkin s U LANL LLNL Lodestar MIT Lehigh U

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N S T X-U

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  1. NSTX-U Supportedby ProgressandPlansfor PedestalPhysics andControl Ahmed Diallo R. Maingi, S.P. Gerhardt, J-WAhn Coll ofWm&Mary Columbia U CompX GeneralAtomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Lehigh U Nova Photonics ORNL PPPL Princeton U PurdueU SNL Think Tank,Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois UMarylandURochester U Tennessee U Tulsa UWashington U Wisconsin XScienceLLC Culham Sci Ctr YorkU Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U KyushuTokai U NIFS Niigata U U Tokyo JAEA Inst forNucl Res, Kiev Ioffe Inst TRINITI ChonbukNatl U NFRI KAIST POSTECH Seoul Natl U ASIPP CIEMAT FOM InstDIFFER ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, CzechRep and theNSTX-UResearchTeam NSTX-UPAC-35Meeting PPPL-B318 June11-13, 2014 NSTX-U

  2. NSTX-UpgradewithenhancedcapabilitieswillsubstantiallyextendH-modepedestalstudiesNSTX-UpgradewithenhancedcapabilitieswillsubstantiallyextendH-modepedestalstudies • Researchmilestonesinvolvingpedestalphysics • R(15-1):AssessH-modeenergyconfinement,pedestal,andscrapeoff layercharacteristicswithhigherBT,IPandNBIheatingpower • IR(15-1): Developandassessthesnowflakedivertorconfigurationand edgepropertiesinNSTX-U • R(16-1):Assessscalingandmitigationofsteady-stateandtransientheat- fluxeswithadvanceddivertoroperationathighpowerdensity NSTX-U

  3. NSTX-UpgradewithenhancedcapabilitieswillsubstantiallyextendH-modepedestalstudiesNSTX-UpgradewithenhancedcapabilitieswillsubstantiallyextendH-modepedestalstudies • FY15: CharacterizetheH-ModepedestalstructureatincreasedBT,Ip, and NBIheatingpower Characterization • Comparewithresults fromNSTX,andemphasizeonpedestalwidthdependenceonpedestal poloidal β • Buildapedestaldatabase for testingEPEDmodelonSTs • Assess thepedestalstabilityinbothstandardandsnowflakeconfigurations • FY15:Identifytheunderlyingmechanismscontrollingthepedestalstructure • – Leverage thehighspatialresolutionedgediagnostics(e.g., BES,ME-SXR, bolometer) • FY16: Experimentswillbeperformedtocontroltheimpurityaccumulationin thepedestalusingthesetools: Control • Lithium granuleinjection(LGI) • 3Dmagneticperturbations forELMpacing • Upwardevaporator • Supersonicgasinjection(SGI) forELM triggeringand fueling • Attempt tostrengthenEdgeHarmonicOscillation(EHO) • Snowflake toreducedivertorerosion, impuritysource this talk Backup NSTX-U

  4. NSTX-Ufacilitiesupgradesenableaccesstonewparameterregimesand uniquecapabilitiesforestablishingthephysicsbasisforST-FNSF • Pressurepedestalheightscaleswiththesquareoftheplasma current • Ip:1.3to2MA • HigherBTforsameq95,higherheatingpowertoreachβpedlimit • – BT: 0.5 to1T, andPNBI:5to10MW(5s)&7.5to15MW(1.5s) • Lowercollisionalityleadingtohigherbootstrapcurrent, whichinturnwill resultinstrongerpeelinginstability drive • Reductionof collisionalitybyfactor2–3 during first 2 years • High-Zplasmafacingcomponents • Pedestal diagnostics:high-resolutionMPTS,BES,bolometers, ME-SXR NSTX-U

  5. NSTX-Ugoal:developpredictivecapabilityforpedestalstructure andevolutionforFNSF MeasuredPed.Height(kPa) 100 • EPED(staticmode)predictslimitingpedestal height andwidthonmultiplehighaspectratio machines NSTX-U NSTX 10 – EPEDisonlyapplicable to thepressure, therefore cannot distinguishindividual transport channels C-Mod DIII-D(C-Modidentity) DIII-D Static ITERprediction (a) 1 • NSTX parameters challenging for EPEDmodel 1 10 100 EPEDPredicted Pedestal Height(kPa) – due tohighq95, stabilityof high-nballooning, and need tocalculaten=1,2peeling-ballooningwhichis challenging forELITE EPED1 Model, DIII-D144977 (with dynamics) 16 Prediction for 14Peeling-BallooningELMonset Pedestal Height (pped, kPa) constraint on pedestal pressure • NSTX-Uwillprovideextensiveand detailedpedestal datainFY15&FY16 to: 12 10 Increasingtime • Extend thepedestalwidthscaling • Characterize thepedestalevolution during ELM cycle 8 6 Kinetic Ballooning constraint on 'VP 0.030.04 Evolution • density and temperatureseparately • comparewithstandardaspectratio 4 0.02 0.050.060.07 0.08 Pedestal Width( ) N – Control andoptimize thepedestal P.B. Snyder, PoP19, 056115(2012) NSTX-U

  6. Outline • Recenthighlights-CollaborationandNSTX • – DIII-D: Pedestal recoverytimescales(bothdensityandtemperature) • andneoclassicalcalculationsin thepedestal(inbackup) • – MAST: PedestalIpscalingandevolution(not shownhere) • C-Mod:Searchforkineticballooningmodes • NSTX:Progressonpedestal edgesimulations, ELMtype characterizations, andon“EnhancedPedestal”H-modeanalysis • NSTX-UplansforFY15&FY16 • Summary NSTX-U

  7. EarlyrecoveryfordensityandtemperaturearesignificantlydifferentEarlyrecoveryfordensityandtemperaturearesignificantlydifferent Freqbands ofinterest Freqbands ofinterest Recovery~ first 10%of anELMcycle • Firstdetailedmeasurementsof the pedestalrecoverydynamicsafter anELM • Clearly thedensityand temperaturegradient recoveryare decoupled • – Suggestingheat transportis thedominant mechanismin saturating theedgepedestal Gradient ne=nePED/neWidth Recovery~ first 50%of anELMcycle recovery Gradient Te=TePED/TeWidth NSTX-U

  8. FirstsystematicmeasurementsofthepedestalrecoveryvsIPforbothintrinsicandpacedELMsFirstsystematicmeasurementsofthepedestalrecoveryvsIPforbothintrinsicandpacedELMs Decouplingofthetemperatureanddensitygradientsathigherplasma current 30 25 Recoverytimes [ms] 20 B=1.9T q95=2.67~6.2 PNBIaverage-3-4MW Temperature gradient 15 Density gradient 10 5 Groebner NF 2009 0 0.8 1 1.2 1.4 Plasma current [MA] 1.6 1.8 NSTX-U

  9. C-Modfindscoherentmagneticfluctuationsconsistentwithkinetic ballooningmode(KBM)andEPED/ELITEmodels andnballooningcontours Unstable Ballooning Stable 500 400 300 200 100 0 0.5 0.4 0.3 0.26 Maaggnetic fluctuationsspectrogram n=10mode Frequency[kHz] Baloo-infinite-nideal ballooningcode • Measured field-aligned electromagneticmodeandpedestal localized that clamppedestal∇Te • Noclearevidenceof suchinstability limiting thepedestalonNSTX 0.22 0.18 0.14 1.11 1.12 1.13 1.14 1.15 Diallo PRL2014 Time [s] NSTX-U

  10. Linear simulations using GENE find NSTX pedestal top is unstable to KBM and micro-tearing Growthratedependenceonβindicates KBMunstableinexperiment 10 2 0 -2 -4 -6 -8 -10 -12 iondiamagnetic (b) (a) direction 3 γ ω HybridTEM-KBM KBM Experiment 2 1 1 microtearing 0 -1 0.1 (c) -2 microtearing θ -3 -14 electrondiamagnetic 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 =0.72 direction NSTX,#139047, 0.01 β -16 β 0.01 0.1 k θρs 1 0.01 0.1 1 kθρs DialloNF 2013 • GENEcalculationswithelectromagneticcontributionareperformedwhereBESmeasurementsarelocalized • – edgepedestalisunstable toKBMinagreement withcalculationsusingGS2by Canik(NSTX)andDickinson(MAST) 10 NSTX-U

  11. NSTXledthe2013FESmulti-machinejoint researchtarget(JRT) • Evaluatestationaryenhancedconfinementregimeswithout largeEdgeLocalizedModes(ELMs) • Identifycorrelationsbetweenedgefluctuationsandtransport • Theresearchaimedtostrengthenthebasisforextrapolation ofstationaryregimeswhichcombinehighenergy confinementwithgoodparticleandimpuritycontrol • NSTX-UwillassessEPHasaleadingcandidatescenariofor accessingveryhighenergyconfinement 11 NSTX-U

  12. EPHisapromisingconfinementregimewithhighH98~1.5-1.6and higherthanstandardH-modeionpedestals H-mode EPH-mode • JRTeffortsenabledanextensive characterizationof EPHdischarges • Ion temperaturegradient ismuchsteeper than inH-mode. • Developsastrong toroidal flowshear, and oftenaverynarrowminimain the flow Ti vs. MajorRadius 0.030 0.025 0.020 0.015 0.010 0.005 Maximumionpedestal gradientnormalizedtoIp 0.000 FT vs. MajorRadius 0 50100150 200 250 -dFT/dR[kHz/m] RotationShear (on thesmall-Rsideof the rotation minima) GerhardtNFatpress2014 NSTX-U

  13. LithiumwallconditioningleadstoeliminationofELMsandsubsequentimpurityaccumulationLithiumwallconditioningleadstoeliminationofELMsandsubsequentimpurityaccumulation nolithium- intrinsicELMs stronglithium - ELM-free 3D pulses lithium+3DRMPELMpacing WhatarethestepstakentoreducethecarbonaccumulationonNSTX-U? - - - 3DRMP(shownabove) EHO(seebackup) Lithiumgranuleinjection NSTX-U

  14. LithiumGranuleInjector(LGI)willbetestedonNSTX-Uto paceELMswithgoalofflushingimpurities TriggeredELMs Natural ELMs • LGIhasbeensuccessfullyappliedonEASTto triggerELMsat 25Hz MansfieldNucl. Fusion(2013) • LGIwillbe testedonNSTX-U tocontrol theimpurityaccumulation • ReduceZeff to2-2.5in thepedestal • Investigate theeffectsof theinjection frequency, granulevelocity, sizeon triggeringefficiencyand impuritycontrol • Extend theinjectionrate to1kHz • Recent collaborationswith DIII-D using lithium dropper: • Lithium dropper resulted inELM-freeperiodsup to~400mswithTeped>1keVand H98<2 • Pepedalmost tripled; nosignof Pradsecularincrease(seebackup) NSTX-U

  15. PedestalResearchplansforFY15 • CharacterizetheH-ModepedestalstructureatincreasedBT,Ip,andNBI heatingpower,shaping,lowercollisionality • Experiments tomeasure thepedestalstructuredynamics • Compare toresults fromNSTX,emphasizingpedestalwidthdependenceon pedestalβ-poloidal • Buildandextend thepedestaldatabase for testingEPEDmodelonSTs • Identify commoncharacteristicsin thephenomenologyof different typesof ELMs • Access thelowcollisionalityregimeandassessitsimpactof thepedestalstability • Lowercollisionalitywilllead tohigherbootstrapcurrent • Establish theEP-Hregimesand furtherinvestigate(inalargerparameterspace) the underlyingphysicsmechanismleading toEPH • Continuetheinvestigationofthepedestalmicroinstabilitiesaffectingthe pedestaldynamics • Leverage thehighspatialresolutionedgediagnostics(e.g., BES,ME-SXR, bolometer) • Re-establish theexistenceof EHOandstudyitsdependencewithcollisionalityand rotationshear(3Dmidplanecoilsand2ndNBI tovaryrotation) NSTX-U

  16. PedestalResearchplansfor FY16 • PerformarangeofexperimentsusingtheLGIto: • TriggerELMs • Establish thedependenceof injectionrate, granulesizeswith typesof ELM • Developaphysicalunderstandingof the triggeringmechanismusingnonlinearELM codes(e.g., JOREK) • Assesstheeffectsoftheupwardevaporatoronthepedestalstructureand impuritycontent;comparewithpreviousNSTXresults • Determine if thereis furtherwideningofpedestalwithincreasedlithium • Establishthe3DmagneticperturbationsforELMpacingandcompare withELMtriggeredviaLGI • Leverage themagneticperturbationand theLGI toassess thenavigabilityof thestability diagram • Supersonicgasinjection(SGI) forELM triggeringand fueling • Develop3DtriggeredEPHandexplorephysicsandimpactofhighedge rotationshear • Stability:explorepotentialdifferencesin pedestal fueling and/or ELM behavior from operation on high-Z vs. C tiles NSTX-U

  17. Goal of measuringpedestalevolutionand controlling it onms-time scaleisfocusofarecentEarlyCareerResearchProposalAward • Expectedavailabilityforphysics research:duringFY2016 run • 50 Laserpulses • Fastpedestalmeasurement usingpulse burstlasersystem (PBLS) • Controlregionusingactuators 5ms~pedestal characteristicrecovery time seebackupformore details NSTX-U

  18. Summary: PedestalresearchinNSTX-UwillcontributetoH-modeunderstandingandcontrolforITERandFNSF • Substantialprogressmadeonunderstandingofpedestal dynamicsthroughcollaborativeresearchandin-depth analysisofNSTXdataduringthepastyear • NSTX-Uwillthoroughlycharacterizeevolutionduring ELMcycle;Validatepredictivemodelsofpressureprofile evolution • Will separateeffectsofdensityandtemperatureprofiles,asneededfor predictivecapabilityandtoprovidecontroloptions • NSTX-Uwillusenewcapabilitiestoeffectivelycontrolthe pedestalforoptimumperformance • LeveragesimilarcontroltoolsdeployedonEASTandDIII-D NSTX-U

  19. Backup NSTX-U

  20. KineticneoclassicalcalculationsusingXGC0capturesnon- MaxwellianiondistributionsinDIII-Dpedestal • Kineticeffectsleadtonon-Maxwellianionenergydistributions • Result: speciesdependentTi anistropyandintrinsicedge flows • Er istherootsolutionthatbalancesneoclassicaliontransport • Balanceionorbit lossagainstneoclassicalpinch • Goodagreement withmeasured “fluid forcebalance”Er whenconsidering diagnosticandkineticeffects • Ti atOutboard Midplane EratOutboardMidplane CERTCθ CERTCϕ XGC0Tθ XGC0Tϕ Self-consistent ErDotted: XGC0fluid Solid: XGC0 fluid+PDF XGC0Te ψN 20 NSTX-U

  21. EdgeHarmonicOscillation(EHO)observedinNSTX pedestalsbuttooweakflushoutimpurity • BESandreflectometeranalysisshow that themodesareveryedgelocalized • ELITEcalculationsshow that thepedestalresidesnear thepeelingboundary • – similar toEHOduringQHmodeinDIII-D • NSTX-Uwillaccesslowcollisionalitywhichincombinationwith the2ndNBIand themidplanecoilswillenablevariationof theedgerotationshearandpotentially re-establishEHO BESData NSTX-U

  22. ELMstriggeredwith3-DfieldsandSGIsuccessfulandsnowflakeconfigurationreducesedgecarbonELMstriggeredwith3-DfieldsandSGIsuccessfulandsnowflakeconfigurationreducesedgecarbon ELMtriggeringwithn=3pulses reference ELMy n=3pulses Canik, PRL2010 Soukhanovskii,APS2010 SGIpulses NSTX-U

  23. ped ELM-freeperiodsupto~400msecobserved,withTe >1keVand ped H98 <2;Pe almosttripled;nosignofPradsecular increase Reference, Lithium H98 Li core ped Te Prad ped ne ped Pe StoredEnergy Time[ms] Time[ms] NSTX-U

  24. Planstomeasurepedestalevolutiontoenableitscontrolonms-time scalesisthefocusofarecentEarlyCareerResearchProposalAward • Goalsofstudy • Determine andcharacterizethe fundamentalmechanismat play that define thepedestal recovery, buildupuntil thenextELM(e.g., C-Mod, DIIID, MAST, plans forNSTX-U) • Developa fastThomsonscatteringsystem forcharacterizingthepedestalrecoverywith high timeresolutionandprovide themeans tocontrolthepedestal • FY2013-2014results/progress • Directevidenceof coherent instabilitylimiting thepedestalevolution • Characterized the timescalesat playduring theearlyrecoveryof thepedestal • Thusfar:procuredphaseIofahybridlasersystemdesignwithPSLatUW(with30Hzbasereprateand1kHzor10kHzreprateburstingphase) • Designreview tobeheldinJuly2014 • Phase II cancommenceonce thelaserheadisdelivered(expectedAugust152014) • Developingreal-timealgorithm forcomputingdensityand temperature • Actuatorsforcontrollingthepedestal • Near termcandidate: LGI,andmolecularclusterinjector(collaboration fromLTX) • Long termcandidate: EHOantenna, ECH/EBW NSTX-U

  25. ELMheatfluxfootprintbecomes morepeakedwithdecreasingnumberof striations;relatedtoNSTXstabilityonlow-ncurrentdrivenstabilityboundary Hightriangularity 5striations Hightriangularity AhnsubmittedPRL2014 Lowtriangularity 0striation Low triangularity • Foragivenlow-n(<4), thewettedareaincreaseswithnumberof striations • – Shapingappears toplayaroleinspreading theheat • ITERalsopredicted tobeonlow-ncurrent drivenboundary–like NSTX? NSTX-U

  26. CouplingoftheNSTX-UHHFWantennatotheplasmawas examinedasmeanstoamplifyEHOmodes(expectedinFY2018) • IPECusedtocomputeplasma displacementsusinganideal plasmaresponsemodel. HHFW – Calculations show that displacements with~1kAcurrent in theHHFWantennamatches theobservedEHOdisplacements. • NSTX-Ucalculationsindicatedthat comparabledisplacementsmaybe achievableatlower-q95 • – Need toassess the βNdependence NSTX Measurements and Calculations NSTX-U NSTX-U Calculations HHFWfieldconfigurationnotfully optimizedforthebestEHOcouplinginNSTX-U NSTX-U

  27. LeveragerecentlyidentifiedlongpulseEPH-modesfor explorationinNSTX-U EarlyExamples short-lived [MaingiJNM2009] FirstextendedEP-Hmode manyconfinement times [MaingiPRL2010] Quiescentlong-durationEPH-mode maintainedforNBheatingandquiescent [GerhardtsubmittedtoNF2014] Density riseduetocarbon impurityaccumulations NSTX-U

  28. EnhancedPedestalH-mode(EP-H)observedwithH98 <1.7,higherthanH-modeiontemperaturepedestal PNBI/10 [MW] Profilecharacterization Density Storedenergy ⌧E ⌧E/⌧H98 D↵ 28 NSTX-U

  29. EnhancedPedestalH-mode(EP-H)observedwithH98 <1.7,higherthanH-modeiontemperaturepedestal PNBI/10 [MW] Profilecharacterization EnhancedPedestalH-mode Density Storedenergy ⌧E ⌧E/⌧H98 D↵ 28 NSTX-U

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