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Title: Blob wakes in NSTX

Abstract

Transient small-scale structures were identified in the wake of blobs moving poloidally through the scrape-off layer of high-powered H-mode plasmas in NSTX, using the gas puff imaging (GPI) diagnostic. These blob wakes had a poloidal wavelength in the range of λ pol = 3.5 ± 0.7 cm, which is significantly smaller than the average blob scale of L pol ~12 cm, and the wakes had a poloidal velocity of V pol = 1.5 ± 1.0 km/s in the electron diamagnetic direction, which is opposite to the blob poloidal velocity in these shots. These wakes were radially localized 0–4 cm outside the separatrix and occurred within ~50 μs after the passage of a blob through the GPI field of view. The clearest wakes were seen when the GPI viewing angle was well aligned with the local B field line, as expected for such small-scale structures given the diagnostic geometry. In conclusion, a plausible theoretical interpretation of the wakes is discussed: the observed wakes share some features of drift waves and/or drift-Alfvén waves which could be excited by the blobs.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Lodestar Research Corp., Boulder, CO (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1558756
Alternate Identifier(s):
OSTI ID: 1543031
Grant/Contract Number:  
AC02-09CH11466; AC52-07NA27344; FG02-02ER54678
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 26; Journal Issue: 7; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Zweben, S. J., Myra, J. R., Diallo, A., Russell, D. A., Scotti, F., and Stotler, D. P. Blob wakes in NSTX. United States: N. p., 2019. Web. doi:10.1063/1.5094872.
Zweben, S. J., Myra, J. R., Diallo, A., Russell, D. A., Scotti, F., & Stotler, D. P. Blob wakes in NSTX. United States. doi:10.1063/1.5094872.
Zweben, S. J., Myra, J. R., Diallo, A., Russell, D. A., Scotti, F., and Stotler, D. P. Wed . "Blob wakes in NSTX". United States. doi:10.1063/1.5094872.
@article{osti_1558756,
title = {Blob wakes in NSTX},
author = {Zweben, S. J. and Myra, J. R. and Diallo, A. and Russell, D. A. and Scotti, F. and Stotler, D. P.},
abstractNote = {Transient small-scale structures were identified in the wake of blobs moving poloidally through the scrape-off layer of high-powered H-mode plasmas in NSTX, using the gas puff imaging (GPI) diagnostic. These blob wakes had a poloidal wavelength in the range of λpol = 3.5 ± 0.7 cm, which is significantly smaller than the average blob scale of Lpol ~12 cm, and the wakes had a poloidal velocity of Vpol = 1.5 ± 1.0 km/s in the electron diamagnetic direction, which is opposite to the blob poloidal velocity in these shots. These wakes were radially localized 0–4 cm outside the separatrix and occurred within ~50 μs after the passage of a blob through the GPI field of view. The clearest wakes were seen when the GPI viewing angle was well aligned with the local B field line, as expected for such small-scale structures given the diagnostic geometry. In conclusion, a plausible theoretical interpretation of the wakes is discussed: the observed wakes share some features of drift waves and/or drift-Alfvén waves which could be excited by the blobs.},
doi = {10.1063/1.5094872},
journal = {Physics of Plasmas},
number = 7,
volume = 26,
place = {United States},
year = {2019},
month = {7}
}

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