Progress towards sustainment of internal transport barriers in DIII-D

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Neutral beam heated discharges with internal transport barriers (ITB) have been observed in most of the world`s major tokamaks including DIII-D, TFTR, JT-60U and JET. Improved core confinement has been observed over a range of q profiles, including negative central magnetic shear (NCS) and weak positive shear. In discharges with an L-mode edge, the duration of ITBs is generally limited to a few energy confinement times ({tau}{sub e}) by low-n MHD activity driven by the steep core pressure gradient or by q{sub min} passing through low-order rational values. In order for ITBs to be useful in achieving a more compact ... continued below

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5 p.

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Rice, B. W.; Ferron, J. R. & Burrell, K. H. July 1998.

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Neutral beam heated discharges with internal transport barriers (ITB) have been observed in most of the world`s major tokamaks including DIII-D, TFTR, JT-60U and JET. Improved core confinement has been observed over a range of q profiles, including negative central magnetic shear (NCS) and weak positive shear. In discharges with an L-mode edge, the duration of ITBs is generally limited to a few energy confinement times ({tau}{sub e}) by low-n MHD activity driven by the steep core pressure gradient or by q{sub min} passing through low-order rational values. In order for ITBs to be useful in achieving a more compact advanced tokamak, the radius of the ITB must be expanded and the pressure gradient must be controlled in order to optimize {beta}{sub N} and the bootstrap alignment. In this paper, the authors discuss the results of recent experiments on DIII-D to produce and sustain ITBs for longer pulse lengths. Three techniques are evaluated: (1) reduction of neutral beam power (P{sub NBI}) and plasma current to form a weaker ITB which can be sustained; (2) use of an ELMing H-mode edge to help broaden the pressure profile and improve MHD instability; (3) modification of the plasma shape (squareness) to achieve smaller ELMs with a lower density pedestal at the edge.

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5 p.

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INIS; OSTI as DE98007298

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  • 25. European Physical Society conference on controlled fusion and plasma physics, Prague (Czech Republic), 29 Jun - 3 Jul 1998

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  • Other: DE98007298
  • Report No.: GA--A22918
  • Report No.: CONF-980678--
  • Grant Number: AC03-89ER51114;AC02-76CH03073;AC05-96OR22464;W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 639767
  • Archival Resource Key: ark:/67531/metadc695274

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  • July 1998

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  • Aug. 14, 2015, 8:43 a.m.

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  • Aug. 1, 2016, 6:38 p.m.

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Rice, B. W.; Ferron, J. R. & Burrell, K. H. Progress towards sustainment of internal transport barriers in DIII-D, article, July 1998; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc695274/: accessed October 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.