Comparative studies of electrostatic turbulence induced transport in presence of resonant magnetic perturbations in RFX-mod

Abstract

Three-dimensional non-axisymmetric magnetic fields are purposely applied to toroidally symmetric fusion plasmas in order to modify transport of heat and particle fluxes to the plasma-facing components (PFCs), and specifically to control and suppress Edge Localized Modes (ELMs) in H-mode tokamak plasmas. This paper presents a comparative study between two magnetic configurations available in the RFX-mod device, namely the original reversed-field pinch configuration and the more recent low-field circular ohmic tokamak. The object of this study is the chaotic edge, which is spontaneous in the RFP configuration and induced by externally applied magnetic perturbations (MPs) in the tokamak. The analogy between the RFX-mod reversed-field pinch and tokamak configuration is developed through experiments with externally applied Resonant Magnetic Perturbations (RMPs). A detailed study of the underlying magnetic topology in both configurations is given through the field line tracing code FLiT. The electrostatic flux profiles turn out to be modulated around the O-point and X-point of the magnetic islands driven by the externally applied perturbations. Furthermore, the evidence of transport induced by small-scale electrostatic turbulence is discussed and the transverse wave numbers characterizing it are identified.

Direct effects of the resonant magnetic perturbation on turbulent transport

“…In particular, the studies of the effects of the RMPs on turbulence and transport are in progress. The experiments have clearly shown the increase of turbulence and of the transport in the presence of RMPs in tokamak plasmas [4]- [7] and in other configurations as RFX [8] and LHD [9]. Theoretical models and numerical simulations have confirmed these effects ([10]- [12] and the references there in)…”

Multiscale interaction between a large scale magnetic island and small scale turbulence

“…Reduction of turbulent fluctuation by loss of the pressure gradient inside the flat magnetic island has been observed in [17,18]. Experimental measurements of the poloidal flow in the vicinity of the magnetic island have been reported in [19,20,21,22,23], and they found that the flow shear across the island can be important in multiscale interactions and consequently in the transport across the island. Recent simulation studies have predicted multiscale interactions via both pressure and flow profiles.…”

Turbulent transport of fast ions in tokamak plasmas in the presence of resonant magnetic perturbations

“…In particular, due to finite Larmor effects [12,13], the E ×B diffusion coefficients decay algebraically at large energies. In fusion devices such as ASDEX Upgrade [14,15], DIII-D [16,17] and others [18,19] it has been found experimentally that the interaction of fast particles with RMPs leads to a substantial increase in radial transport and, consequently, fast ion loses.…”