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LP1.006

Supported by. LP1.006. 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

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LP1.006

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  1. Supported by LP1.006 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 2-D Imaging of Edge Turbulence in NSTX and Alcator C-Mod J.L. Lowrance, S.J. Zweben, J.L. Terry, R.J. Maqueda, D.P. Stotler, D.A. D’Ippolito, J.R. Myra, J. Boedo, C.Bush, R. Maingi, T. Munsat, D. Swain, J. Wilgen, B. LaBombard, O. Grulke, S. Kaye, B. LeBlanc, H. Mynick, N. Pomphrey, V. Mastrocola, G. Renda, A. Keesee, N. Nishino, and the NSTX Team and the Alcator C-Mod Team 45th Annual Meeting of Division of Plasma Physics American PhysicalSociety October 27 – 31, 2003 Albuquerque, New Mexico

  2. Abstract High speed 2-D images of edge turbulence in NSTX and Alcator C-Mod have been made using an ultra-fast CCD camera from Princeton Scientific Instruments, Inc. This camera views fluctuations in the neutral line emission from He or D gas puffs near the outer midplane where roughly 5 eV < Te < 50 eV. The movies show a variety of interesting structures and motion with a resolution of 160 x 80 pixels per frame for 28 frames at up to 1 million frames/sec (PSI-4 camera). Typical movies will be shown, analyzed, and compared with other edge turbulence data from these machines.

  3. Princeton Scientific Instruments Inc. Ultra-Fast Cameras • Obtained for use at NSTX and C-Mod through an SBIR • PSI-3 used in ‘00-’01, PSI-4 in ‘02-03, PSI-5 in ‘03-‘04 • For company information see http://www.prinsci.com

  4. NSTX Edge Turbulence • See edge turbulence “filaments” aligned along B field line with short (few cm) scale across B field line Magnetic structure of edge plasma LANL fast camera view 10 µsec exposure NSTX R = 85 cm a = 68 cm A = 1.25 I ≤ 1.5 MA B ≤ 6 kG 5 MW NBI 6 MW ICRH bT ≤ 35%

  5. Gas Puff Imaging Diagnostic in NSTX • Looks at He1(578.6 nm) from gas puff I  none f(ne,Te) • View along B field line to see 2-D structure  B GPI view 16x32 cm

  6. 2-D Imaging of NSTX Edge Turbulence Single frame taken in HeI (587.6 nm) light, from PSI-4 camera movie at 100,000 frames/sec and10 µsec/frame for 28 frames/shot (see Laptop movie) out 200 separatrix 100 0 Separatrix is near “5 cm” HeI peaks @ Te ≈ 10 eV where: d≈ .5)dne/ne + (0.7)dTe/Te Zweben, Maqueda et al, PPPL-3795 (March ‘03) submitted to NF

  7. Comparisons of GPI with Other Diagnostics • Small regions of GPI image were sampled at 500 kHz and compared with probe (UCSD) and reflectometer (ORNL) • Frequency spectra were very similar before and during puff x reflectometer before puff • reflectometer during puff o GPI during puff x probe before puff • probe during puff o GPI during puff Power (rel.) Frequency (kHz) Frequency (kHz)

  8. 200 x 100 16 cm 0 out OUT Typical Image Sequences in NSTX Ohmic L-mode H-mode

  9. out out OUT Blob-like Motion in NSTX Images Outward blob Upward blob Outward + Downward Downward + Outward

  10. out OUT Wave-like Motion in NSTX Images wave wave + blob bloblike wave counter- moving blobs

  11. Ohmic L-mode H-mode Statistics of Blob Motion in NSTX • Track local maxima as “blobs” vs. 2-D space vs. time • No correlations of Vpol and Vrad or Vrad and Intensity

  12. Comparison with “Blob” Model in NSTX See poster [LP1.070]: Theory and Experimental Analysis of Blobs in the NSTX Boundary Plasma J.R. Myra, D.A. D'Ippolito (Lodestar Research Corp.), D.P. Stotler, S.J. Zweben ( PPPL), R. Maqueda, NSTX Team

  13. Comparison of BOUT with GPI in NSTX See poster [LP1.008]: Boundary turbulence Simulations and Experimental comparisons in NSTX* W.M. Nevins, R. H. Bulmer, X.Q. Xu (LLNL), S. Zweben, D.P. Stotler (PPPL), R. Maqueda (LANL)

  14. Deriving Velocity Fields from NSTX Movies • Local velocity fields in 2-D can be estimated from cross- correlation in time, as used in fluid PIV (T. Munsat) • Velocity fields might be used to estimate local transport

  15. DEGAS 2 Modeling of GPI in NSTX See poster [LP1.007]: Neutral Transport Simulations of Gas Puff Imaging Experiments on NSTX D.P. Stotler, B. LeBlanc, S.J. Zweben (PPPL), J.R. Myra, D.A. D'Ippolito (Lodestar Research Corp.), R.J. Maqueda (LANL), S.A. Sabbagh (Columbia U.)

  16. Gas Puff Imaging Diagnostic on C-Mod • Looks at Da(656 nm) from gas puff I  none f(ne,Te) • View along B field line to see 2-D structure  B GPI View 6 cm x 6 cm

  17. 2-D Imaging of Alcator C-Mod • Often see “blobs” moving outward through outer edge, typically at 105 cm/sec (e.g. 2 cm / 20 µsec) Alcator C-Mod R = 67 cm a = 23 cm A = 3 I ≤ 1.5 MA B ≤ 80 kG 5 MW ICRH b ≈ 1% [Terry, Zweben et al, Phys. Plasmas ‘03]

  18. Blobiness Increases Toward Wall in C-Mod • Sequence of movies taken at different times during the same shot shows “blobiness” seems to increase toward the outer wall (location of Da light emission is changing vs. time) -see Laptop movie near separatrix near limiter scrape-off OUT 6 cm Limiter Limiter Limiter

  19. Side View of C-Mod Edge Turbulence • View Da light emission horizontally from side of tokamak • Turbulence filaments aligned nearly along B (see Laptop) Single frame from movie with 6 µsec exposure time in Da light emission

  20. Correlation of GPI and Probe in C-Mod • Langmuir probe and GPI aligned along B @ ≈ 3 m distance • Fairly high correlation between GPI light and Isat (≈ 0.3) corrleation between GPI diodes and Isat [CO1.003] Spatiotemporal characterization of turbulent fluctuations in the SOL of Ohmic discharges in C-Mod O. Grulke, J.L. Terry, B. Labombard (MIT PSFC), S.J. Zweben (PPPL)

  21. Comparison with NLET Simulations in C-Mod • Non-Local Edge Turbulence code run for one C-Mod case • Good agreement between NLET and GPI data kpol spectrum NLET code: K. Hallatschek See: J.L. Terry, S.J. Zweben et al, IAEA 2002(IAEA-CN94/EX/P5-10) J.L. Terry, S.J. Zweben et al Phys. Plasmas 10, 1739 (2003)

  22. Plans for Future 2-D Imaging • • Use 300 frame PSI-5 to capture L-H transition and ELMS • • Look at turbulence near X-point with new tangential view • • Look at high-field side turbulence with inner wall gas puff • • Measure zonal flows and parallel flows with two-line-filter • Doppler shift technique (Paul, RSI ‘03) • • Look at smaller and larger spatial scales k >> 1 and << 1 • Make detailed comparisons between GPI data and theory / simulation

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