An X-point ergodic divertor

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A new ergodic divertor is proposed. It utilizes a system of external (n = 3) coils arranged to generate overlapping magnetic islands in the edge region of a diverted tokamak and connect the randomized field lines to the external (cold) divertor plate. The novel feature in the configuration is the placement of the external coils close to the X-point. A realistic design of the external coil set is studied by using the field line tracing method for a low aspect ratio (A {approx equal} 3) tokamak. Two types of effects are observed. First, by placing the coils close to the ... continued below

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Pages: (25 p)

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Chu, M.S.; Jensen, T.H.; La Haye, R.J.; Taylor, T.S. & Evans, T.E. October 1, 1991.

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Description

A new ergodic divertor is proposed. It utilizes a system of external (n = 3) coils arranged to generate overlapping magnetic islands in the edge region of a diverted tokamak and connect the randomized field lines to the external (cold) divertor plate. The novel feature in the configuration is the placement of the external coils close to the X-point. A realistic design of the external coil set is studied by using the field line tracing method for a low aspect ratio (A {approx equal} 3) tokamak. Two types of effects are observed. First, by placing the coils close to the X-point, where the poloidal magnetic field is weak and the rational surfaces are closely packed only a moderate amount of current in the external coils is needed to ergodize the edge region. This ergodized edge enhances the edge transport in the X-point region and leads to the potential of edge profile control and the avoidance of edge localized modes (ELMs). Furthermore, the trajectories of the field lines close to the X-point are modified by the external coil set, causing the hit points on the external divertor plates to be randomized and spread out in the major radius direction. A time-dependent modulation of the currents in the external (n = 3) coils can potentially spread the heat flux more uniformly on the divertor plate avoiding high concentration of the heat flux. 10 refs., 9 figs.

Physical Description

Pages: (25 p)

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OSTI; NTIS; INIS; GPO Dep.

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  • International Atomic Energy Agency (IAEA) technical committee meeting on research using small tokamaks, Hefei (China), 3-8 Oct 1991

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  • Other: DE92002298
  • Report No.: GA-A-20682
  • Report No.: CONF-9110259--1
  • Grant Number: AC03-89ER53277
  • Office of Scientific & Technical Information Report Number: 5071341
  • Archival Resource Key: ark:/67531/metadc1057764

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  • October 1, 1991

Added to The UNT Digital Library

  • Jan. 22, 2018, 7:23 a.m.

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  • Jan. 29, 2018, 11:28 p.m.

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Chu, M.S.; Jensen, T.H.; La Haye, R.J.; Taylor, T.S. & Evans, T.E. An X-point ergodic divertor, article, October 1, 1991; United States. (https://digital.library.unt.edu/ark:/67531/metadc1057764/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.