Progress towards sustainment of advanced tokamak modes in DIII-D

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Improving confinement and beta limits simultaneously in long-pulse ELMy H-mode discharges is investigated. The product {beta}{sub N}H{sub 98y} serves as a useful figure-of-merit for performance, where {beta}{sub N} {triple_bond} {beta}/(I/aB) and H{sub 98y} is the ratio of the thermal confinement time relative to the most recent ELMy H-mode confinement scaling established by the ITER confinement database working group. In discharges with q{sub 0} {approximately} 1 (no sawteeth) and discharges with q{sub min} > 1.5 and negative central magnetic shear, {beta}{sub N} {approximately} 2.9 and H{sub 98y} {approximately} 1.4 are sustained for up to 2 s. Although peaked profiles are observed, ... continued below

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24 p.

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

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Description

Improving confinement and beta limits simultaneously in long-pulse ELMy H-mode discharges is investigated. The product {beta}{sub N}H{sub 98y} serves as a useful figure-of-merit for performance, where {beta}{sub N} {triple_bond} {beta}/(I/aB) and H{sub 98y} is the ratio of the thermal confinement time relative to the most recent ELMy H-mode confinement scaling established by the ITER confinement database working group. In discharges with q{sub 0} {approximately} 1 (no sawteeth) and discharges with q{sub min} > 1.5 and negative central magnetic shear, {beta}{sub N} {approximately} 2.9 and H{sub 98y} {approximately} 1.4 are sustained for up to 2 s. Although peaked profiles are observed, steep internal transport barriers are not present. Further increases in {beta}{sub N} in these discharges is limited by neoclassical tearing modes (NTM) in the positive shear region. In another recently developed regime, {beta}{sub N} {approximately} 3.8 and H{sub 98y} {approximately} 1.8 has been sustained during large infrequent ELMs in non-sawtoothing discharges with 1{sub 0} {approximately} 1. This level of performance is similar to that obtained in ELM-free regimes such as VH-mode. The limitation on {beta}{sub N} and pulse length in these discharges is also the onset of NTMs.

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24 p.

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INIS; OSTI as DE99001352

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  • 17. IAEA fusion energy conference, Yokohama (Japan), 19-24 Oct 1998

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  • Other: DE99001352
  • Report No.: GA--A22999
  • Report No.: CONF-981064--
  • Grant Number: AC03-89ER51114;AC02-76CH03073;AC05-96OR22464;W-7405-ENG-48
  • Office of Scientific & Technical Information Report Number: 296837
  • Archival Resource Key: ark:/67531/metadc677556

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  • December 1998

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  • July 25, 2015, 2:20 a.m.

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  • Aug. 1, 2016, 6:38 p.m.

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Rice, B. W.; Burrell, K. H. & Ferron, J. R. Progress towards sustainment of advanced tokamak modes in DIII-D, article, December 1998; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc677556/: accessed September 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.