Thermal characterization of helical (QSH) states in the RFX reversed Field Pinch
Abstract
Recent experiments in the RFX machine, have demonstrated the existence of helical equilibria in the RFP, which are obtained both transiently and in steady state. During such states, relatively large, bean-shaped, m=1 structures in the SXR emissivity profiles are observed, and the MHD spectrum is characterized by the presence of a single dominant mode (helical states are also dubbed Quasi Single Helicity states) whose poloidal phase is well correlated with the position of m=1 SXR structure. During transient QSH states driven by Pulsed Poloidal Current Drive, the thermal profiles show a poloidal asymmetry, corresponding to the heating of the m=1 structure: this evidence suggest that the improvement of the thermal insulation is related to the helical topology of the magnetic field. We will in particular address the thermal properties of QSH: by studying the electron temperature and density profiles and therefore the pressure profiles, we will analyze the role played by the (helical) hot core and by the axisymmetric edge on the formation, the sustainment and of the confinement properties of such states. An investigation of the regimes more favourable to the formation of the helical hot core (internal transport barrier) and a comparison between stationary, transient and spontaneous QSH states will be presented.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 1999
- Bibcode:
- 1999APS..DPP.GP167M