Intermittent Divertor Filaments in the National Spherical Torus Experiment and Their Relation to Midplane Blobs

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While intermittent filamentary structures, also known as blobs, are routinely seen in the low-field-side scrape-off layer of the National Spherical Torus Experiment (NSTX) (Ono et al 2000 Nucl. Fusion 40 557), fine structured filaments are also seen on the lower divertor target plates of NSTX. These filaments, not associated with edge localized modes, correspond to the interaction of the turbulent blobs seen near the midplane with the divertor plasma facing components. The fluctuation level of the neutral lithium light observed at the divertor, and the skewness and kurtosis of its probability distribution function, is similar to that of midplane blobs ... continued below

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Maqueda, R. J. & Stotler, D. P. May 19, 2010.

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While intermittent filamentary structures, also known as blobs, are routinely seen in the low-field-side scrape-off layer of the National Spherical Torus Experiment (NSTX) (Ono et al 2000 Nucl. Fusion 40 557), fine structured filaments are also seen on the lower divertor target plates of NSTX. These filaments, not associated with edge localized modes, correspond to the interaction of the turbulent blobs seen near the midplane with the divertor plasma facing components. The fluctuation level of the neutral lithium light observed at the divertor, and the skewness and kurtosis of its probability distribution function, is similar to that of midplane blobs seen in Dα; e.g. increasing with increasing radii outside the outer strike point (OSP) (separatrix). In addition, their toroidal and radial movement agrees with the typical movement of midplane blobs. Furthermore, with the appropriate magnetic topology, i.e. mapping between the portion of the target plates being observed into the field of view of the midplane gas puff imaging diagnostic, very good correlation is observed between the blobs and the divertor filaments. The correlation between divertor plate filaments and midplane blobs is lost close to the OSP. This latter observation is consistent with the existence of ‘magnetic shear disconnection’ due to the lower X-point, as proposed by Cohen and Ryutov (1997 Nucl. Fusion 37 621).

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  • Report No.: PPPL-4516
  • Grant Number: DE-ACO2-09CH11466
  • DOI: 10.2172/981708 | External Link
  • Office of Scientific & Technical Information Report Number: 981708
  • Archival Resource Key: ark:/67531/metadc1013371

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  • May 19, 2010

Added to The UNT Digital Library

  • Oct. 14, 2017, 8:36 a.m.

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  • Nov. 6, 2017, 5:51 p.m.

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Maqueda, R. J. & Stotler, D. P. Intermittent Divertor Filaments in the National Spherical Torus Experiment and Their Relation to Midplane Blobs, report, May 19, 2010; Princeton, New Jersey. (digital.library.unt.edu/ark:/67531/metadc1013371/: accessed July 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.