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Fast Probe Results and Plans

Fast Probe Results and Plans. By J. Boedo For the UCSD and NSTX Teams. Probe Installed and Commissioned. Location is 6/8” below midplane. 11 deg angle. 6.8”. New head and tips to accommodate curvature and heat flux. Thermal Conductivity Thermalgraph Tips (parallel) 800 W/mK

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Fast Probe Results and Plans

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  1. Fast Probe Results and Plans By J. Boedo For the UCSD and NSTX Teams J. Boedo, UCSD

  2. Probe Installed and Commissioned Location is 6/8” below midplane 11 deg angle 6.8” J. Boedo, UCSD

  3. New head and tips to accommodate curvature and heat flux Thermal Conductivity Thermalgraph Tips (parallel) 800 W/mK Copper 401 W/mK POCO graphite 72 W/mK J. Boedo, UCSD

  4. Existing Probe Head has 10 Tips • Tips in blue will be active on day one, the rest implemented as upgrades (if funded) • Fluctuations to 1 MHz • Two Vf tips used for Epol (and fluctuations) • Two Vf tips used as Er (and fluctuations) >> Reynolds Stress • One tip as Isat >> ne • Two tips as double probe (Te and Ne profiles) Vf1 Epol Isat Vf2 Er Vf3 Vf4 Te fluct Bt Mach1 Double Probe Mach2 J. Boedo, UCSD

  5. Data Taken at High Spatial and Temporal Resolution Insertion completed in 100 ms. ~30 ms in plasma Time resolution for Te and Ne is 1 ms Time resolution for fluctuations is 1 micro sec Spatial resolution is 1.5-2 mm (tip size + probe motion) J. Boedo, UCSD

  6. Within the limited shot space, density and power were varied. So scaling is inconclusive • So far: • decreases in H mode with power 2.5>1.5 cm • Will obtain wider operating space in the future and produce scalings J. Boedo, UCSD

  7. H-mode Radial Electric Field Flat in SOL J. Boedo, UCSD

  8. Fluctuation Quantities to Characterize in NSTX Need to add Te fluct capability J. Boedo, UCSD

  9. Harmonic Diganostic Probe V R1 Ampli- tude detector Amp C1 C3 fdrive= 400 kHz R2 V_fast I C2 400 kHz Bandpass filter Ampli- tude detector Pearson coil Amp Amp 250 W RF amp I2 800 kHz Bandpass filter Ampli- tude detector Amp Amp I_fast Dummy transmission line I_min V_min I /I2 Analog divider Compa- rator Compa- rator Adder Tunable LPF Analog multiplier Ref Ref Analog multiplier Te_slow J. Boedo, UCSD

  10. Harmonics Technique Current to a DC-floating probe driven by sinusoidal voltage can be expressed as a series of sinusoidal harmonics [1]: where - amplitude of mth harmonic - Bessel functions of integer order k For eU0/kTe << 1: Thus Te can be determined from the ratio of the amplitudes of 1st and 2nd harmonics The error of this approximation for eU0/kTe= 1 is only about 5% [1] [1] Boedo et al,Rev. Sci. Instrum.70 (1999), 2997 J. Boedo, UCSD

  11. Need to Include Magnetic component Particle Flux Reynolds Stress (neglecting ion pressure fluctuations) Heat Flux Parallel Current Flux Helicity Flux J. Boedo, UCSD

  12. Normalized N fluctuations very large J. Boedo, UCSD

  13. Radial Turbulent Flux Lower in H-mode Value is ~3-5 1017 cm-2 s-1 J. Boedo, UCSD

  14. Intermittent Plasma Events Pervasive J. Boedo, UCSD

  15. Power Spectrum Comparison Power spectrum vs f (in kHz) from probe data during gas injection (solid circles) and without(x) and comparison to that obtained form the GPI system (open circles). Note that the power spans y 4 orders of magnitude indicating excellent S/N ratio. J. Boedo, UCSD

  16. Intermittency (Radial Convective Transport) Lower in H-Mode L-Mode 109033 H-Mode 109052 Intermittency is very strong in NSTX! J. Boedo, UCSD

  17. Intermittency (Radial Convective Transport) Lower in H-Mode L-Mode 109033 H-Mode 109052 Intermittency is very strong in NSTX! J. Boedo, UCSD

  18. L-Mode 109033 Density is highly intermittent Rate of bursts is ~1E4 Poloidal field is much less intermittent Coherent modes show in Etheta Instantaneous flux is 1-3E15 cm-2s-1 J. Boedo, UCSD

  19. H-Mode 109052 Density is intermittent (ELMs?) Rate of bursts is 2E3 Poloidal field is much less intermittent Coherent modes show in Etheta Instantaneous flux is ~2E15 cm-2s-1 J. Boedo, UCSD

  20. Initial Reynolds Stress and Bicoherency Measurements H-Mode Codes Written and Tested L-Mode J. Boedo, UCSD

  21. Bispectrum H-mode L-Mode f3=f1+f2 f3=f1-f2 J. Boedo, UCSD

  22. Bicoherency H-mode L-Mode J. Boedo, UCSD

  23. Profile Conclusions • Edge/SOL profiles available with high spatial (2-2.5 mm) resolution • Limited to 1086xx, 1089xx, 109032-109062 • Fully calibrated data for 109032-xxx062 • NSTX profiles seem different from larger aspect ratio devices • Te profile in the edge/SOL is flat at 25-30 eV • Ne profile has a very long decay length. Reduced by power! • H-mode Er profile flat in SOL • How do flat Te profiles are maintained? • Do we have (more) anomalous radial transport? (intermittency) • Adding fast Te diagnostic J. Boedo, UCSD

  24. Future Work and Goals • Data obtained in L and H-mode. SOL length scales with power. Ongoing • Many puzzles need addressing • Features usually associated with LCFS vicinity are different in NSTX, such as a potential well, steep H-mode profiles, etc Ongoing • Intermittency is quite strong in NSTX (very strong radial transport?) • Need to quantify electrostatic turbulence and Intermittency (enough to explain strong transport?) Codes just ported for electrostatic turbulence, ongoing for intermittency! • Bicoherency and Reynolds Stress codes just finished. Investigate energy cascading and self-organized flows • Need to quantify electromagnetic components of transport • Upgraded head partially designed and to be built in FY04 J. Boedo, UCSD

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