1,721,881 research outputs found
Analysis of vertical displacement events in tokamaks removing the evolutionary equilibrium assumption
No full textAn Integral Formulation for the Electrodynamics of Metallic Carbon Nanotubes Based on a Fluid Model
No full textAn integral formulation to model, in the frequency domain, the electromagnetic response of three-dimensional (3-D) structures formed by metallic carbon nanotubes and conductors, within the framework of the classical electrodynamics, is described. The conduction electrons of the metallic nanotube are modeled as an infinitesimally thin cylindrical layer of compressible fluid, whose dynamics are described by means of the linearized hydrodynamic equations. The resulting integral equations are solved numerically by the finite element method using the facet elements and the null-pinv decomposition. The proposed formulation is applied to study carbon nanotube interconnects and dipole antennas and some related results are outlined. The solutions highlight the high-frequency effects due to the electron inertia and the fluid pressure. In particular, since the kinetic inductance matrix dominates over the magnetic one, proximity effects are negligible
The Coupling Surface Method for the Solution of Magnetoquasi-Static Problems
No full textIn this paper, we present a novel methodology for decoupling the solution of the magnetoquasi-static equations in subdomains through a coupling surface and related equivalent currents. In particular, the solution outside the coupling surface is condensed with a suitable boundary condition. Different formulations can be used in each subdomain, hence allowing the most convenient approach to be used in each case. Some examples of the application are presented, showing the effectiveness of the method
Two-port characterization of two-wire interconnects based on full-wave electromagnetic model
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Prediction of the Growth Rates of VDEs in JET
No full textIn this paper we show that the effect of the saddle currents in the rigid sectors slows down the vertical instability of JET elongated plasmas with respect to estimates based on pure axisymmetric models. This, together with an accurate description of the passive structures, significantly improves the agreement between the theoretical predictions and the experimental results. Linearized models taking into account the three-dimensional effects of the eddy currents have been applied to various JET pulses; the growth rates have been estimated within an accuracy of less than 5% for plasmas with a growth time longer than 2 ms. This model can be used for JET and extended to ITER-FEAT to provide a reliable test bed for assessing the performance of the vertical control system and obtain an estimate of the loads on the structures during vertical displacement events (VDEs) and plasma disruptions
A Lagrangian approach to shape inverse electromagnetic problems
No full textThis paper presents a completely lagrangian approach able to solve shape inverse (optimization and identification) electromagnetic problems. A first order deterministic minimization technique combined with a lagrangian finite element approach is used. Theoretical and numerical advantages and drawbacks of such a method are discussed, and some applications are presented
Optimization of the magnetostatic field in SMES devices
No full textThe aim of this paper is to show how SMES devices, if arranged with more than two magnetic dipoles, can perform better. The analysis is carried out either considering or not the presence of a ferromagnetic shield, In the latter case a shape optimization of the iron shield is performed using a combined stochastic/deterministic method. The paper shows bow advantages can be taken by evaluating the sensitivity matrix of the iron shape optimization by means of a Lagrangian formulation of the Maxwell's equations
Power-law characteristic for 3-D macroscopic modeling of superconductors via an integral formulation
No full textThree-dimensional electromagnetic analysis of cable-in-conduit conductors for fusion applications
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