A spectral model for interchange transport in tokamak scrape-off layers

Abstract

The intermittent convection of plasma filaments, or blobs, is commonly considered to be responsible of the transport across flux surfaces in scrape-off layer (SOL) of fusion devices. Isolated filament models are generally derived from vorticity conservation in order to deduce the speed of these filaments, showing good predictions against experimental measurements on individual filaments, but yet unable to predict the total flux associated to these events. In this work, the isolated filament approach is extended to a model of poloidal spectra for both potential and density fluctuations. An heuristic closure is used to derive analytical descriptions of these spectra are obtained, resulting in predictions for a wide variety of observables from fluctuation levels, correlation lengths and associated fluxes. Results are verified against flux-driven simulations and then validated against a broad set of experimental measurements from circular plasma. Predictions for the SOL width take the form of the engineering scaling law that finds sound agreement with experimental scaling built from multi-machine databases.