Transient regimes of impurity ion transport and electron heat diffusivity in Tore Supra ohmic discharges following nickel laser blow-off injection
Nickel has been injected in ohmic Tore Supra discharges with and without activation of the ergodic divertor (ED). The Ni ion transport is studied by means of an impurity transport code simulating soft X-ray brightness and emissivity time evolutions. Radial profiles of the diffusion coefficient D and of the inward convection velocity V are obtained. Two previously reported conclusions are confirmed: the presence of a central core with reduced transport coefficients and, with the ED activated, the necessity of introducing a peripheral transport barrier. To simulate satisfactorily in both experimental conditions the initial phase of the Ni ion inflow before the first inverted sawtooth, it is necessary to increase transiently the impurity ion transport coefficients during the first milliseconds after the injection. By comparison of experimental and simulated bolometric signals it is possible to verify quantitatively the available calculations of the radiative losses for Ni, the observed discrepancy by a factor of two being discussed. With a heterodyne radiometer (monitoring the electron temperature) the inwards propagating cold wave, following the Ni injection, has been observed. Both with and without ED, good simulations of the cold wave propagation are obtained using a predictive transport model.
Bibliographic Reference: Report: EUR-CEA-FC-1606 EN (1997) 37pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez-Durance (FR)
Record Number: 199711259 / Last updated on: 1997-10-10
Original language: en
Available languages: en