Self-organized 3D equilibrium formation and its feedback control in RFX-mod

P. Piovesan, D. Bonfiglio, L. Marrelli, A. Soppelsa, M. Spolaore, D. Terranova

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The reversed-field pinch exhibits a strong tendency to self-organize into a helical equilibrium as the plasma current is increased. The helical reversed-field pinch is characterized by reduced magnetic stochasticity and by the formation of electron internal transport barriers. The paper gives an update on recent experimental and modelling work on helical states in RFX-mod (Sonato et al 2003 Fusion Eng. Des. 66 161), also discussing similarities with 3D equilibria in tokamaks. The helical equilibrium is modelled with 3D codes developed for stellarators, such as VMEC/V3FIT. The reconstructed safety factor profile has low or reversed magnetic shear in the core, which may be related to transport barrier formation. A significant extension of the RFX-mod database to high current and density confirms the dependence observed before of various helical state properties on macroscopic quantities. Even under conditions where it does not form spontaneously, such as at low current or high density, the 3D magnetic equilibrium can be stimulated and robustly controlled with external fields applied by an extensive set of non axi-symmetric coils. An advanced magnetic feedback algorithm that compensates for error fields induced by eddy currents in the 3D wall structures has been developed. This work stimulated similar experiments in RFX-mod run as a tokamak, where external 3D fields are applied to control a m = 1/n = 1 helical equilibrium. © 2014 EURATOM.
Original languageEnglish
Article number064006
Pages (from-to)-
JournalNuclear Fusion
Issue number6
Publication statusPublished - 2014
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Piovesan, P., Bonfiglio, D., Marrelli, L., Soppelsa, A., Spolaore, M., & Terranova, D. (2014). Self-organized 3D equilibrium formation and its feedback control in RFX-mod. Nuclear Fusion, 54(6), -. [064006].