The NSTX Research Program and Collaboration Opportunities

1. Supported by Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics NYU ORNL PPPL PSI SNL UC Davis UC Irvine UCLA UCSD U Maryland U New Mexico U Rochester U Washington U Wisconsin Culham Sci Ctr Hiroshima U HIST Kyushu Tokai U Niigata U Tsukuba U U Tokyo Ioffe Inst TRINITI KBSI KAIST ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching U Quebec The NSTX Research Program and Collaboration Opportunities E.J. Synakowski PPPL Alcator C-Mod Ideas Forum December 2, 2004

2. Experimental collaboration Theory-experiment coupling Unique NSTX plasma properties provide scientific leverage in all major areas of toroidal confinement research Strengthen the scientific basis for fusion energy Edge transport & stability Core transport & turbulence MHD: stability & helicity injection Wave/particle interactions Test theory by isolating important physics and challenging models at their extremes of applicability

3. Control tools to test physics & increase operating space focus for FY ‘05-‘07 Innovative diagnostics Inter-device studies enabling High b impact onturbulence, waves, MHD Unique edge B structure science High Vflow/VAlfvén Large super-Alfvénic ni NSTX research is entering a phase of advanced diagnostic implementation and advanced control Optimize long-pulse, high b Strengthen physics understanding Strengthen physics basis with advanced measurements & control at high b & low A Assess high b, low A physics with passive control • Take maximal scientific advantage of ST plasma characteristics through novel diagnostics and new control tools, and targeted inter-device studies

4. NBCD bootstrap EBW psi 40% bT with ~100% INI, tpulse >> tskin, demands development of new tools and understanding their underlying physics • 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% bT , INI = 100%, tpulse >> tskin 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? bootstrap NBCD EBW grad-pth q(0) q(min) Kessel, TSC IAEA 2004

5. Helicity injection Active feedback coils enabling Strong shaping science Flows Dynamo physics Nonlinear fast ion MHD NTM physics MHD & macroscopic plasma behavior Optimize stability of high b Develop startup techniques Deepen physics understanding of stability & reconnection Physics of active control Expand operating space Passive stability limits & mode characterization 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 C-Mod/NSTX opportunities include • Error field studies • Fast ion physics • Edge stability (discussed later)

6. Rotation effects are strong in NSTX plasmas Rotational shear also strong candidate for internal mode saturation W. Park, J. Menard

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

9. 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

10. Particle control: lithium Electron thermal transport: High k scattering Ion, electron transport: low k imaging e-m effects, low & hi k science Transport & turbulence (core) NB vs HHFW heating q profile & reverse shear enabling Optimize confinement + JBS in long-pulse, high b Extend physics understanding of turbulence to unity b Confinement optimization Role of b + Er in c & turbulence Global scalings Local c Edge turbulence NSTX transport physics • Role of b: onset of electromagnetic effects broadens theory/experiment comparisons • Electron transport: Broad range of k for theory tests C-Mod/NSTX research opportunities • High k comparisons at low & high b and the onset of e-m effects • Core ITBs with RF • Dimensionless similarity?

11. R0=101 cm change (%) 127 cm 131 cm 134 cm 137.5 cm t (ms) 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 ce transport is rapid, it can be modified • Why the flat center? • Collaborative core transport similarity experiments through ITPA (MAST, DIII-D) LeBlanc, R. Bell, Kaye Rapid cold pulse propagation following ELM Te Faster Ip ramp Stutman, JHU

12. 1.0 k (cm-1) 10 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.) Contact hpark@pppl.gov

13. EBW tube. Launcher development Heat low Ip plasmas for ramp-up NBI at modest B enabling HHFW wave physics from antenna to core EBW physics: mode conversion & f(v) modification science Super-Alfvénic particles & MHD Waves & energetic particles Reduce V-s through JBS and direct CD Extend physics understanding of waves in overdense plasmas Coupling startup techniques to ramp-up Wave physics in overdense plasmas HHFW heating, phasing, & CD EBW emissions Opportunities with MIT/ C-Mod program • Strong RF theory & modeling effort at present, including ongoing EBW theory research • Direct measures of fast wave deposition NSTX wave-particle physics • HHFW, EBW: wave coupling, propagation & deposition for overdense plasmas (for ST, RFP) • EBW: Ohkawa current drive with high trapping fraction

14. HHFW Absorption Depends on Antenna Phasing Edge ion heating, parametric decay of HHFW HHFW modulated to assess % absorption Hot component Cold component Biewer, APS invited 2004 Absorption k||=14 m-3 80% 7 m-1 (ctr) 75% -7 m-1 (co) 40% 3 m-1 10% Evidence for parametric absorption processes found in spectroscopy, RF probes Contact jrwilson@pppl.gov ckphillips@pppl.gov

15. 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?

16. 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

17. Radiative divertor regimes Lithium studies for influx control Optimize ELMs enabling Pedestal-core connection Pedestal stability at low A SOL transport & turbulence L-H transition physics science Plasma boundary interfaces Optimize high b, long pulse regimes through pedestal modification Assess boundary control needs for steps beyond NSTX Power balance Heat flux scaling Pedestal & ELM character Lithium pellets & coatings Fueling studies SOL transport Boundary physics opportunities • Advanced heat and particle flux management techniques relevant to all toroidal confinement concepts • SOL transport: intermittency & shear Alfvénic turbulence C-Mod/NSTX opportunities • Different edge Bp/B T • Different values of B, ne, Te…

18. Improved diagnostics are allowing details of ELM characteristics to emerge Type V Type I • 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 Small, filamentary, perturbation Larger low n perturbation Contact rmaingi@pppl.gov ktritz@pppl.gov

19. 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

20. 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? Zweben L mode Probes: Boedo Umansky, LLNL BOUT simulations underway based on measured profiles & NSTX geometry (preliminary)

21. 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 Liquid lithium module: decision following coatings studies e-beam for Li coatings in ‘06 Li pellets: injector commissioned in ‘04 • Develop deposition techniques in ‘05 • Under ALIST group of VLT • Would represent a revolutionary solution for both power and particle handling Contact hkugel@pppl.gov,rkaita@pppl.gov boedo@fusion.gat.com

22. 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

23. 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

25. NSTX research for ‘05 - ‘07 is well aligned with the fusion program’s scientific priorities and supports strategic goals FESAC Theme: Understand the role of magnetic structure on confinement, & plasma pressure limits FESAC Theme: Learn to use energetic particles & e-m waves to sustain and control high temperature plasmas NSTX Stability pressure limits & magnetic reconnection vs. A, shape, profile, q & flows, for internal & external modes with Vflow/VA < 0.4 & unity b; 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 _ Determine Most Promising Configurations Develop New Materials, Components, & Technologies Demonstrate Feasibility with Burning Plasmas Develop Understanding and Predicitve Capability Microscopic ion, electron, and tearing turbulence measurement & theory comparison over wide range in b, flows, and magnetic shear, with good average curvature and high trapping Physics of ELMs, pedestal, SOL turbulence & high divertor heat flux, with large in/out asymmetry; Li coatings & liquid surface interactions with plasma. • FESAC Theme: Learn to control the interface between a 100 million degree plasma and its room temperature surroundings FESAC Theme: Understand & control the processes that govern confinement of heat, momentum, and particles

26. 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 • Vq, Vf with HHFW & prior to ohmic H modes • Needed to reconstruct Er & profile • Vq measurements deeper in the core will be developed for ‘06 R. Bell

27. NSTX research led to an expansion of operating space in 2004 Reduced latency improved vertical control at high-k, high-bT Capability for higherk, dallowed higher IP/aBT Significantly more high-bT (bN=6.8 %mT/MA achieved) More routine highk, d Longer current flattop duration tpulse = t(>0.85 Ip,max) Time of peak bT