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Digital archive of theses discussed at the University of Pisa


Thesis etd-10272015-114259

Thesis type
Tesi di dottorato di ricerca
Thesis title
Rigid-Rotor Profiles in an Inductively Driven Field-Reversed Configuration
Academic discipline
Course of study
tutor Prof. Giammanco, Francesco
commissario Prof. Pegoraro, Francesco
commissario Dott. Buratti, Paolo
commissario Dott. Romè, Massimiliano
commissario Dott. Wessel, Frank
  • nuclear fusion
  • plasma diagnostics
  • plasma modeling
  • plasma rotation
Graduation session start date
Release date
A practical description, based on the Rigid-Rotor Model, has been given for a Field-Reversed Configuration (FRC) produced using a central flux coil assembly to drive the plasma current inductively. This model is a time independent, 1-D analytic description which assumes that the plasma rotates with uniform angular frequency, independent of radius.
The model provides an analytic description for the radial profiles of plasma density, magnetic field and electric field at equilibrium. An experiment was configured to measure these radial profiles with appropriate diagnostic instrumentation. Data fitting validates the Rigid-Rotor Model predictions for the specific parameter regime investigated, on this particular configuration. The profiles are found to be Rigid-Rotor-like and suggest that the plasma is rotating with a sizable ion current component; this rotation also seems to develop early in time, rather than being driven during the equilibrium phase.
A hybrid MHD code was used to simulate the acceleration, formation, evolution, and equilibrium of a flux-coil produced FRC. The simulation retains the MHD equations for the radial and axial components, and uses a two-fluid-like description for the azimuthal component of the ion motion. The model is 2-D and is applied to a plasma where the ion Larmor radius is comparable to the dimensions of the simulation boundaries for the confinement vessel, and the electron Larmor radius is small. The inductive electric field accelerates the ions, producing an azimuthal current and a quasi-equilibrium state with a Rigid-Rotor-like structure. The simulation produces results qualitatively similar to the experimental measurements, however several discrepancies are identified and analyzed.
These results provide guidance for analyzing past, and future, experimental and theoretical investigations of the FRC, where plasma spin-up is observed in the azimuthal direction. A few possible future developments and applications of this research are also presented.