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National Spherical Torus Experiment Facility / Diagnostic Overview

Supported by. National Spherical Torus Experiment Facility / Diagnostic Overview. 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

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National Spherical Torus Experiment Facility / Diagnostic Overview

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  1. Supported by National Spherical Torus ExperimentFacility / Diagnostic Overview 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 JAERI Ioffe Inst TRINITI KBSI KAIST ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching U Quebec Masayuki Ono For the NSTX Team 46th Annual Meeting of Division of Plasma Physics, American Physical Society November 15 - 19, 2004 Savannah, Georgia

  2. Designed to Study High-TemperatureToroidal Plasmas at Low Aspect-Ratio Achieved Parameters Aspect ratio A 1.27 Elongation  2.6 Triangularity  0.8 Major radius R0 0.85m Plasma Current Ip 1.5MA Toroidal Field BT0 0.6T Solenoid flux 0.7Vs Auxiliary heating & current drive: NBI (100kV) 7 MW RF (30MHz) 6 MW CHI 0.4MA Pulse Length 1.1s Stored Energy 400 kJ bT ~ 40%

  3. Operational and Physics Advances Have Led to Significant Progress Towards Goal of High-bT, Non-Inductive Operation H-mode plasma • tIp flattop ~ 3.5tskin • tW flattop ~ 10 tE • bT>20%, bN>5, tE/tE,L>1.5 for ~10 tE • IBS/Ip = 0.5, IBeam/Ip = 0.1 fBS = IBS/Ip = 0.5 e1/2bpol bT = <p>/(BT02/2m0)

  4. Research Topics to Achieve Long-Pulse, High Performance Plasmas Are Identified • Enhanced shaping improves ballooning stability • Mode, rotation and error field control allows high beta • NBI and bootstrap sustain most of current • HHFW heating contributes to bootstrap • EBW provides off-axis current& stabilizes tearing modes • Particle and wall control maintains proper density

  5. NSTX had a very productive FY 04 Run • Successfully operated for 21.1 weeks with 2460 plasmas • Met the Joule milestone of 18 weeks and programmatic goal of 20 weeks • Significantly expanded plasma operational regimes toward the NSTX longer term goals: • High k ~ 2.5 plasma controlled by faster plasma control system • Simultaneous high bT - high j-bootstrap regimes expanded • Effective plasma pulse duration (tpulse Ip/ITF) doubled • Meeting all the FY 04 research milestones: • High beta plasma (bT ≥ 25%) sustained for longer than 2 tE • MSE-CIF now yielding core current profile information • Core and edge fluctuations measured and characterized • EBW emission measurement suggests good coupling efficiency • New solenoid-free start-up experiments conducted with “transient” CHI and with outer PF coils

  6. TF-Joints issues being resolved • Gradual joint resistance increase observed in many stressed joints at 4.5 kG • Further joint monitoring revealed greater than anticipated flag movements • For machine safety, TF limited to 3 kG during the last month of operation • Out-of-spec flag movement traced to not-fully-penetrated epoxy fill • Through R&D, a reliable full-penetration epoxy-fill technique developed • Other improvements implemented • Appropriate design reviews are being conducted NSTX plasma operations to resume in Feb. 2005

  7. MHD Tools to reach near ideal MHD limits

  8. Improved Plasma Control System Opened Operating Window During 2004 Campaign Capability for higherk, dallowed higher IP/aBT Significantly more high-bT (bN=6.8 %mT/MA achieved) Reduced latency improved vertical control at high-k, high-bT More routine highk, d Longer current flattop duration tpulse = t(>0.85 Ip,max) Time of peak bT

  9. New PF 1A Coils to improve plasma shaping 114465 PF1A Goal of 2005 Achieved 2004 • Shorter PF 1A is needed to improve the plasma shaping control (k = 2.5 and d = 0.8) for advanced ST operations. • Due to the success of high k operation this year, the new PF 1A coil will be installed this year ahead of schedule. • Should be available for FY 05 run starting in Feb. 05.

  10. Vacuum Vessel Conducting Plates Resistive Wall Mode Growth Rate (s-1) Internal Sensors Columbia U, GA, PPPL Active Control Will Enable Study of Wall Mode Interactions with Error Fields & Rotation at High bT

  11. Ex-Vessel Feedback Control Coil System Status • • A pair of the Ex-Vessel Feedback Control Coils installed and energized with the preprogrammed power supply in July, 2004. • • Several experiments were performed: • –locked mode control, • plasma rotation control, • error field amplification, • Resistive Wall Modes physics. Full Ex-Vessel Feedback Control Coil System is scheduled to be available for the FY 05 experimental run.

  12. Transport and Confinement Measuring Fluctuations to gain understanding of plasma transport Pfusion ~ H5-7

  13. Measured magnetic field pitch in a ST for the first time MSE-CIF j(r) diagnostic Nova Photonic Inc MSE Multistage Lyot Filter • Calibrated in situ and achieved the desired statistical errors of 0.2°/0.4° at 4.5/3.0 kG • Initial 8 ch data were collected with 4 ch activated at one time. • MSE data being incorporated into EFIT and other codes. • time(sec) • MSE-CIF measured q(0) and Raxis • • q(0) ~ 0.8 before ~1 after crash • • Raxis shift inboard ~ 2 cm after crash • • 5 msec resolution 8 ch will be available for the FY 05 run and increased to 12 - 14 ch.

  14. Reflectometry Turbulence Measurements UCLA Reflectometer • Array of microwave reflectometer horns • Aligned perpendicular to magnetic flux surfaces Correlation length measurements

  15. Fast X-ray Camera Reveals Core Electron Dynamics t=0 t=270ms t=90ms t=180ms Images with time resolution down to ~ 2 µs CCD camera Pinholes and Be foils Image intensifier inside magnetic shield Image of core n=1 tearing mode PSI

  16. 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) • Access to ETG possible! • Major installation this opening. High k scattering Luhmann (UC Davis), Munsat (U. Colorado) Mazzucato, Park, Smith (Princeton U.) UCD

  17. Non-Inductive Sustainment HHFW Off-axis Heating and CD EBW CD for profile control*

  18. & Multiple Roles of HHFW • Bulk plasma heating to enhance bootstrap currents in advanced ST Operations • Plasma start-up and current ramp-up • Super-Alfvénic energetic particle physics (UCI) - HHFW modification of NBI fast ion distribution function - TAE mode stablization • Edge physics for RF - Anomalous edge ion heating - Phase dependent heating efficiency - Parametric instabilities 12 antennas powered by 6 MW sources ORNL, UCI, MIT, GA, CompX

  19. EBWs Can Generate Critical Off-Axis Current Drive in NSTX at High b NSTX, b = 40% • ~ 100 kA of off-axis CD needed to sustain b ~ 40% in NSTX • Cannot use ECCD in NSTX since wpe/wce ~ 3-10 • Modeling indicates that EBWCD can provide needed current • EBWCD may also assist startup and stabilize NTM's • 4 MW, 28 GHz EBWCD system planned for NSTX 0 r/a 0 1 Charles Kessel (PPPL) Tokamak Simulation Code Comp-X

  20. NSTX, bT = 42% Strong Diffusion Near Trapped-Passing BoundaryEnables Efficient Ohkawa Current Drive CompXGENRAY/CQL3D

  21. 1 MW “Proof-of-Principal” EBW System Tests Viability of Heating & Current Drive in NSTX • ~ 750 kW EBW power delivered to plasma --> Use EBWCD to locally drive 30-40 kA • If 1 MW system is successful increase RF power to 4 MW with addition of three more gyrotrons, transmission lines & launchers by --> Provide 3 MW of EBW power in the plasma & Generate > 100 kA 1 MW (CPI or Gycom)

  22. Power and Particle Handling NSTX has largest “P/R” in tokamaks/STs comparable to ITER

  23. Gas Puff Imaging Diagnostic viewing area ≈ 25x25 cm spatial resolution ≈ 1-2 cm separatrix RF limiter Typical image Using Princeton Scientific Instruments PSI-5 camera 250,000 frames/sec @ 64 x 64 pixels/frame 300 frames/shot, 14 bit digitizer, intensified PSI, Nova Photonics

  24. Fast probe provided edge density and temperarure profile ne rises faster than Te UCSD

  25. Outer divertor not detached yet LLNL

  26. AXLE FEEDTHRU LOAD PORT PROPELLENT PORT OUTBOARD VIEW 400 BARREL TURRET Lithium Pellets Injection to Control Particle Recycling • Capability for injecting solid pellets (<1 – 5 mg) & powder (micro-pellets) • 10 – 200 m/s radial injection • 1 – 8 pellets per discharge • 400 pellet capacity • Develop optimized scenarios Lithium vapor spreading along the center-stack Lithium Pellet moving through plasma after entering at 296ms In-board gas injector H. Kugel Lithium “vapor ball” surrounding pellet as it approaches the center-stack

  27. Supersonic gas jet penetrates well through a thick scrape-off layer CHERS camera DEGAS 2 Neutral transport modeling reproduces observed features 114449 Preliminary fueling efficiency estimate shows ~ 3 - 4 times improvement over gas puff LLNL

  28. NSTX is developing ITER/BP relevant time resolved surface deposition monitors Deposition over 4 shots 112014-017. deposition temperature • Quartz microbalance shows time resolved deposition on NSTX in geometry typical of a diagnostic mirror - results show significant deposition after plasma discharge. • Novel electrostatic surface particle detector works well in air and vacuum environments. • First time-resolved measurements of surface dust in tokamaks. C. Skinner

  29. Solenoid-Free Start-Up Tokamaks and STs must eliminate OH solenoid Coaxial Helicity Injection Outer poloidal field start-up

  30. Capacitor Bank for Transient-CHI Start-Up • • Successfully installed and commissioned new 2 kV, 100 kJ capacitor bank. • • Conducted initial experiments: • Reduced the required gas pressure for a successful plasma break down by a factor of 3. • Toroidal plasma currents of up to 150 kA were generated by this technique without induction from the central solenoid. • High current multiplication ratio; a record current multiplication of 40 was achieved in NSTX for the first time. • • Direct gas and ECH injection into the injector region implemented to facilitate plasma initiation. Absorber Injector Univ. Washington

  31. Solenoid-free Start-up with Outer Poloidal Field Coils Three scenarios being investigated J. Menard Improved preionization and PF coil waveforms to be optimized

  32. Research Tool Development on NSTX Supports Fusion and Plasma Sciences • Expand MHD operation space: RWM and PF 1A coil systems • Understand confinement: Current Profile, X-rays, Fluctuation diagnostics • Explore super-Alfvenic energetic ion physics: HHFW as a new tool • Gain understanding of HHFW heating and current drive • Develop new efficient edge current drive tool: EBW • Arrays of research tools for heat and particle control • Develop practical solenoid-free start-up tools: CHI and outer PF coils

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