The effect of current profile changes on confinement in the DIII-D tokamak

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Experiments in the DIII-D tokamak have demonstrated that the effect of changes in the current profile on plasma confinement varies with the discharge shape. The results are similar in many respects to those from other tokamaks. In all cases, a rapid change in the plasma current in an L-mode, circular or moderately elongated, discharge has been used to produce a transient change in the current density profile. Although the detailed results vary among tokamaks, it is generally observed that during and immediately following a negative plasma current ramp, the stored energy does not follow the L-mode scaling that predicts that ... continued below

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4 p.

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Ferron, J. R.; Lao, L. L. & Taylor, T. S. May 1, 1992.

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  • General Atomic Company
    Publisher Info: General Atomics, San Diego, CA (United States)
    Place of Publication: San Diego, California

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Description

Experiments in the DIII-D tokamak have demonstrated that the effect of changes in the current profile on plasma confinement varies with the discharge shape. The results are similar in many respects to those from other tokamaks. In all cases, a rapid change in the plasma current in an L-mode, circular or moderately elongated, discharge has been used to produce a transient change in the current density profile. Although the detailed results vary among tokamaks, it is generally observed that during and immediately following a negative plasma current ramp, the stored energy does not follow the L-mode scaling that predicts that confinement should be proportional to the total plasma current. The stored energy changes on the time scale of the relaxation of the current density profile rather than the shorter time scales of the energy confinement time or the change in the total current. Because of the discharge having capability of the DIII-K tokamak it has been possible to extend these current ramp experiments beyond the L-mode, moderate elongation case to highly elongated double-null divertor discharges in H-mode. In separate experiments, a rapid change in the discharge elongation has also been used to vary the current density profile. This paper shows that the dependence of the plasma confinement on the current profile changes when the discharge shape is changed. This variation with discharge shape provides evidence for a model that predicts that changes in the local magnetic shear resulting from the changes in the current profile can result in decreased local transport.

Physical Description

4 p.

Notes

OSTI; NTIS; INIS; GPO Dep.

Source

  • ICPP 92: International conference on plasma physics,Innsbruck (Austria),29 Jun - 3 Jul 1992

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  • Other: DE92016256
  • Report No.: GA-A--20913
  • Report No.: CONF-920610--7
  • Grant Number: AC03-89ER51114
  • Office of Scientific & Technical Information Report Number: 10158760
  • Archival Resource Key: ark:/67531/metadc1390085

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Office of Scientific & Technical Information Technical Reports

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  • May 1, 1992

Added to The UNT Digital Library

  • Nov. 28, 2018, 2:33 p.m.

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  • Feb. 11, 2019, 1:11 p.m.

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Ferron, J. R.; Lao, L. L. & Taylor, T. S. The effect of current profile changes on confinement in the DIII-D tokamak, article, May 1, 1992; San Diego, California. (https://digital.library.unt.edu/ark:/67531/metadc1390085/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.