Computational analysis of ion orbital loss in diverted positive- And negative-triangularity tokamaks

Y. Nishimura, F. L. Waelbroeck, L. J. Zheng

Research output: Contribution to journalArticle

Abstract

The mechanism of ion orbital loss in diverted negative-triangularity (NT) tokamaks is significantly different from that of positive-triangularity (PT) tokamaks. The orbital loss from the edge of NT tokamaks can be quite large, because the separatrix X-point is located on the outboard side, meaning that trapped ions crossing the separatrix are lost to the inboard divertor plate after a mirror reflection on the side of the strong magnetic field. NT tokamaks have difficulties in building up steep pressure gradients in the edge regions. In contrast, the majority of trapped ions crossing the separatrix in PT tokamaks survive (through complete banana motions) without reaching the X-point region. For NT tokamaks, topological changes in the trapped ion trajectories can be achieved in the presence of the radial electric field, thus reducing the orbital loss, whereas for PT tokamaks, the orbital loss is relatively insensitive to the radial electric field.

Original languageEnglish
Article number5131157
JournalPhysics of Plasmas
Volume27
Issue number1
DOIs
Publication statusPublished - 2020 Jan 1

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All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

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