Two-dimensional turbulence cross-correlation functions in the edge of NSTX

Zweben, S. J. ; Stotler, D. P. ; Scotti, F.; Myra, J. R.
Issue date: 2017
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Zweben, S. J., Stotler, D. P., Scotti, F., & Myra, J. R. (2017). Two-dimensional turbulence cross-correlation functions in the edge of NSTX [Data set]. Princeton Plasma Physics Laboratory, Princeton University.
  author      = {Zweben, S. J. and
                Stotler, D. P. and
                Scotti, F. and
                Myra, J. R.},
  title       = {{Two-dimensional turbulence cross-correla
                tion functions in the edge of NSTX}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2017,
  url         = {}

The 2-D radial vs. poloidal cross-correlation functions of edge plasma turbulence were measured near the outer midplane using the gas puff imaging (GPI) diagnostic on NSTX. These correlation functions were evaluated at radii r= 0 cm, ±3 cm, and ±6 cm from the separatrix and poloidal locations p=0 cm and ±7.5 cm from the GPI poloidal center line for 20 different shots. The ellipticity ε and tilt angle φ of the positive cross- correlation regions, and the minimum negative cross-correlation “cmin” and total negative over positive values “neg/pos” were evaluated for each of these cases. The average results over this data set were ε=2.2±0.9, φ=87±34o (i.e. poloidally oriented), cmin= -0.30±0.15, and neg/pos=0.25±0.24. Thus there was significant variation in these correlation results within this database, with dependences on the location within the image, the magnetic geometry, and the plasma parameters. Possible causes for this variation are discussed, including the misalignment of the GPI view with the local B field line, the magnetic shear of field lines in the edge, the poloidal flow shear of the turbulence, blob-hole correlations, and the neutral density ‘shadowing’ effect in GPI.

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