Common features of core electron-root confinement in helical devices

M. Yokoyama, H. Maassberg, C. D. Beidler, V. Tribaldos, K. Ida, F. Castejón, T. Estrada, A. Fujisawa, T. Minami, T. Shimozuma, Y. Takeiri, J. Herranz, S. Murakami, H. Yamada

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)


The characteristics of core electron-root confinement (CERC) in helical devices are illustrated using results from four different experiments: the Compact Helical System, Large Helical Device, TJ-II, and Wendelstein 7-AS, Common features include strongly peaked electron temperature profiles and large positive radial electric fields Er in the core region for discharges with sufficient central electron cyclotron heating (ECH). Such observations are consistent with a transition to the electron-root solution of the ambipolarity condition for Er, a feature of neoclassical theory that is unique to nonaxisymmetric configurations. The magnetic topology of the configuration plays a role in this transition, and thresholds are found for the particle density and ECH power, in accordance with neoclassical expectations. Neoclassical theory alone cannot explain all observations, however, as CERC formation can also be influenced by ECH-driven convective fluxes of localized electrons and by the presence of magnetic islands in the core region. This is the first report describing collaborative activities within the framework of the International Stellarator Profile Data Base.

Original languageEnglish
Pages (from-to)327-342
Number of pages16
JournalFusion Science and Technology
Issue number3
Publication statusPublished - Oct 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • General Materials Science
  • Mechanical Engineering


Dive into the research topics of 'Common features of core electron-root confinement in helical devices'. Together they form a unique fingerprint.

Cite this