Flow and shear behavior in the edge and scrape-off layer of L-mode plasmas in National Spherical Torus Experiment

Sechrest, Y.; Munsat, T.; D’Ippolito, D. A.; Maqueda, R. J.; Myra, J. R.; Russell, D.; Zweben, S. J.

doi:10.1063/1.3533435

Title: Flow and shear behavior in the edge and scrape-off layer of L-mode plasmas in National Spherical Torus Experiment

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3533435· OSTI ID:1076474

Sechrest, Y. ^[1]; Munsat, T. ^[1]; D’Ippolito, D. A. ^[2]; Maqueda, R. J. ^[3]; Myra, J. R. ^[2]; Russell, D. ^[2]; Zweben, S. J. ^[3]

Univ. of Colorado, Boulder, CO (United States)
Lodestar Research Corp., Boulder, CO (United States)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Fluctuations in the edge and scrape-off layer (SOL) of L-mode plasmas in the National Spherical Torus Experiment (NSTX) as observed by the gas puff imaging (GPI) diagnostic are studied. Calculation of local, time resolved velocity maps using the Hybrid Optical Flow and Pattern Matching Velocimetry (HOP-V) code enables analysis of turbulent flow and shear behavior. Periodic reversals in the direction of the poloidal flow near the separatrix are observed. Also, poloidal velocities and their radial shearing rate are found to be well correlated with the fraction of D_α light contained in the SOL, which acts as a measure of turbulent bursts. The spectra of GPI intensity and poloidal velocity both have a strong feature near 3 kHz, which appears to correspond with turbulent bursts. This mode exhibits a poloidal structure with poloidal wavenumber of 7.7 m^-1 for GPI intensity and 3.4 m^-1 for poloidal velocity, and the poloidal velocity fluctuations near 3 kHz remain coherent over length scales in excess of the turbulent scales. Furthermore, recent SOL Turbulence (SOLT) simulations find a parameter regime that exhibits periodic bursty transport and shares many qualitative similarities with the experimental data. Strong correlations between the shearing rate and the turbulent bursts are observed for time periods of ~ 2 ms, but the relationship is complicated by several factors. Finally, measurements of the radial profiles of the Reynolds shear stresses are reported. These radial profiles exhibit many similarities for several shots, and a region with positive radial gradient is seen to be coincident with local flow shear.

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Research Organization:: Univ. of Colorado, Boulder, CO (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: AC02-09CH11466; FG02-08ER54995; SC0001966

OSTI ID:: 1076474

Journal Information:: Physics of Plasmas, Vol. 18, Issue 1; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 23 works

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References (20)

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Cited By (3)

Edge transport studies in the edge and scrape-off layer of the National Spherical Torus Experiment with Langmuir probes Boedo, J. A.; Myra, J. R.; Zweben, S. Physics of Plasmas, Vol. 21, Issue 4 https://doi.org/10.1063/1.4873390	journal	April 2014
Observation of quasi-coherent edge fluctuations in Ohmic plasmas on National Spherical Torus Experiment Banerjee, Santanu; Diallo, A.; Zweben, S. J. Physics of Plasmas, Vol. 23, Issue 4 https://doi.org/10.1063/1.4946871	journal	April 2016
Invited Review Article: Gas puff imaging diagnostics of edge plasma turbulence in magnetic fusion devices Zweben, S. J.; Terry, J. L.; Stotler, D. P. Review of Scientific Instruments, Vol. 88, Issue 4 https://doi.org/10.1063/1.4981873	journal	April 2017

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