Inference of electron heat conductivity from the propagation of a temperature perturbation in the outer confinement region of a Tokamak

The propagation of a heat pulse yields information on the average electron heat conductivity, e, in the layer through which the pulse propagates. In particular, it is possible to infer e from the time elapsed until the temperature perturbation reaches its maximum on different radii, tp(r). In this paper, a discussion is presented of some frequently used simple models and of the errors introduced by a number of assumptions made. – Discussed is the influence of a fixed temperature at the boundary, of the shape of the initial perturbation, of pulse pile-up, of temperature equilibration between electrons and ions, of radiative losses, and of the local changes in the Ohmic power input. Cases with a spatially varying χe are studied numerically. – It is found that the use of the simplest model always yields an overestimation of χe