3-D discrete dispersion relation, numerical stability, and accuracy of the hybrid FDTD model for cold magnetized toroidal plasma

The Finite-Difference Time-Domain (FDTD) method in cylindrical coordinates is used to describe electromagnetic wave propagation in a cold magnetized plasma. This enables us to study curvature effects in toroidal plasma. We derive the discrete dispersion relation of this FDTD scheme and compare it with the exact solution. The accuracy analysis of the proposed method is presented. We also provide a stability proof for nonmagnetized uniform plasma, in which case the stability condition is the vacuum Courant condition. For magnetized cold plasma we investigate the stability condition numerically using the von Neumann method. We present some numerical examples which reproduce the dispersion relation, wave field structure and steady state condition for typical plasma modes

An analysis of the hybrid finite-difference time-domain scheme for modeling the propagation of electromagnetic waves in cold magnetized toroidal plasma

To explore the behavior of electromagnetic waves in cold magnetized plasma, a three-dimensional cylindrical hybrid finite-difference time-domain model is developed. The full discrete dispersion relation is derived and compared with the exact solutions. We establish an analytical proof of stability in the case of nonmagnetized plasma. We demonstrate that in the case of nonmagnetized cold plasma the maximum stable Courant number of the hybrid method coincides with the vacuum Courant condition. In the case of magnetized plasma the stability of the applied numerical scheme is investigated by numerical simulation. In order to determine the utility of the applied difference scheme we complete the analysis of the numerical method demonstrating the limit of the reliability of the numerical results

Ex and In Situ Reactivity and Sorption of Sélénium in Opalinus Clay in the Presence of a Sélénium Reducing Microbial Community

International audience79Se is a critical radionuclide conceming the safety of deep geological disposai of certain radioactive wastes in clay-rich formations. To study the fate of sélénium oxyanions in clayey rocks in the presence of a sélénium reducing microbial community, in situ tests were performed in the Opalinus Clay at the Mont Terri Rock Laboratory (Switzerland). Furthermore, biotic and abioticbatch tests were performed to assess Se(VI) and Se(IV) reactivity in the presence of Opalinus Clay and/or stainless steel, in order to support the interprétation of the in situ tests. Geochemical modeling was applied to simulate Se(VI) réduction, Se(IV) sorption and solubility, and diffusion processes, This study shows that microbial activity is required to transform Se(VI) into more reduced and sorbing Se species in the Opalinus Clay, while in abiotic conditions, Se(VI) remains unreactive. On the other hand, Se(IV) can be reduced by microorganisms but can also sorb in the presence of clay without microorganisms. In situ microbial réduction of Se oxyanions can occur with électron donors provided by the clay itself. If microorganisms would be active in the clay surrounding a disposai facility, microbial réduction of leached Se could thus contribute to the overall rétention of Se in clayey host rocks

Application of the hybrid explicit/implicit finite-difference time-domain method (FDTD) for electromagnetic computations in cold magnetized toroidal plasma /

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