Enhanced transport of impurity ions and electron heat in Tore Supra ohmic discharges following nickel laser blow-off injection
Nickel has been injected into ohmic Tore Supra discharges with and without activation of the ergodic divertor (ED). The nickel ion transport is studied by means of an impurity transport code, and the radial profiles of the diffusion coefficient D and of the inward convection velocity V are obtained by simulating the soft X-ray brightness and emissivity time evolutions. The simulations confirm the presence of a central core with reduced transport coefficients and, with the ED activated, the necessity of introducing a peripheral transport barrier. To make satisfactory simulations in both experimental conditions of the initial phase of the nickel ion inflow before the first inverted sawtooth, it is necessary to increase transiently the diffusion coefficient during the first few milliseconds after the injection. By comparison of the experimental and simulated bolometric signals, it is possible to verify quantitatively the available calculations of the global radiative losses for nickel. The inward propagating cold wave, following the nickel injection, has been observed with a heterodyne radiometer. Both with and without the ED, good simulations of the cold wave propagation are obtained using a predictive non-local transport model, previously successfully tested in the Joint European Torus during transient regimes.
Bibliographic Reference: Article: Nuclear Fusion, Vol. 38 (1998) No. 2, pp. 189-206
Record Number: 199810709 / Last updated on: 1998-06-08
Original language: en
Available languages: en