Modelling of pellet injection experiments with Onsager-symmetric transport relations

Abstract

The formalism of non-equilibrium thermodynamics is applied to the problem of radial transport in tokamak plasmas. Phenomenological relations between generalized forces and fluxes, consistent with the empirical Alcator scaling, are suggested. — A simple 1-D transport model incorporating these relations is shown to reproduce the salient features of recent pellet injection experiments on Alcator-C: a drop in the central temperature preceeding pellet penetration, rapid (< 1 ms) peaking of the density profile, a marked rise in the energy confinement time immediately following injection and persistence of the state of high confinement and peaked density for a time longer than the initial confinement time. The same model reproduces a saturation of Alcator scaling when the density profile becomes flat, as is observed in high density, edge fuelled Alcator-C discharges.