Non-linear instability of DIII-D to error fields

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Otherwise stable DIII-D discharges can become nonlinearly unstable to locked modes and disrupt when subjected to resonant m = 2, n = 1 error field caused by irregular poloidal field coils, i.e. intrinsic field errors. Instability is observed in DIII-D when the magnitude of the radial component of the m = 2, n = 1 error field with respect to the toroidal field is B{sub r21}/B{sub T} of about 1.7 {times} 10{sup {minus}4}. The locked modes triggered by an external error field are aligned with the static error field and the plasma fluid rotation ceases as a result of the ... continued below

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Pages: (8 p)

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La Haye, R.J. & Scoville, J.T. October 1, 1991.

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Description

Otherwise stable DIII-D discharges can become nonlinearly unstable to locked modes and disrupt when subjected to resonant m = 2, n = 1 error field caused by irregular poloidal field coils, i.e. intrinsic field errors. Instability is observed in DIII-D when the magnitude of the radial component of the m = 2, n = 1 error field with respect to the toroidal field is B{sub r21}/B{sub T} of about 1.7 {times} 10{sup {minus}4}. The locked modes triggered by an external error field are aligned with the static error field and the plasma fluid rotation ceases as a result of the growth of the mode. The triggered locked modes are the precursors of the subsequent plasma disruption. The use of an n = 1 coil'' to partially cancel intrinsic errors, or to increase them, results in a significantly expanded, or reduced, stable operating parameter space. Precise error field measurements have allowed the design of an improved correction coil for DIII-D, the C-coil'', which could further cancel error fields and help to avoid disruptive locked modes. 6 refs., 4 figs.

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Pages: (8 p)

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OSTI; NTIS; INIS; GPO Dep.

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  • IAEA technical committee meeting on the avoidance and control of tokamak disruptions, Abindgon (United Kingdom), 10-12 Sep 1991

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  • Other: DE92002479
  • Report No.: GA-A-20653
  • Report No.: CONF-9109252--2
  • Grant Number: AC03-89ER51114
  • Office of Scientific & Technical Information Report Number: 5003244
  • Archival Resource Key: ark:/67531/metadc1055765

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  • October 1, 1991

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  • Jan. 22, 2018, 7:23 a.m.

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  • Jan. 29, 2018, 10:26 p.m.

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La Haye, R.J. & Scoville, J.T. Non-linear instability of DIII-D to error fields, article, October 1, 1991; United States. (https://digital.library.unt.edu/ark:/67531/metadc1055765/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.