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The reconstruction of the Plasma Boundary (PB) in fusion reactors is a critical task in several applications, including plasma control and several off-line studies of the plasma conPgurations. A widely shared dePnition for PB is the Last Closed Magnetic Surface (LCMS) within the vacuum vessel. In the limits of plasma equilibrium conditions, the PB reconstruction should imply the solution of the coupled electro-mechanical plasma equations. The problem is rather complex also in axisymmetric geometry and the solution requires numerical computations not compatible with the needs of a real time response. The problem is more and more complex in fully 3D geometries; therefore, some simpliPed purely electromagnetic approaches have been proposed, including the Ptting of magnetic measurements or the equivalent plasma currents. In any case, in 3D geometry, the LCMS reconstruction is very time-consuming because, despite new algorithms have reduced their complexity [1], the 3D Magnetic Surfaces (MSs) tracking is very demanding. In this paper a new very effective algorithm is proposed. The limiter conPgurations are treated in 2 steps: (a) a preliminary analysis of the Prst wall to select the points with a vanishing normal Peld component; (b) the tracking of all the MSs including one of these points and the LCMS selection. The divertor conPgurations are identiPed with an iterative algorithm inspired by the bisection approach: at (k+1)-th iteration, the LCMS is looked for between the larger closed and smaller not closed surfaces at k-th iteration. In both cases, large benePts are derived from the availability of a parallel computing architecture to carry out the simultaneous construction of a full set of MSs. The paper discusses the application of the new methodology to various JET conPgurations.

Active magnetic shielding of finite domains benefits of a direct effective solution based on the concept of stream function on the domain boundary. In linear systems the solution is flexible and effective when the geometry admits decomposition in eigenfunctions. The paper extends the approach to more complex geometries, by introducing an intermediation domain where the eigenfunctions are available in analytical form.

Magnetic field map in magnetically confined thermonuclear fusion devices must be carefully controlled, in order to achieve desired performance. Residual error fields, which are in any case present, must be reduced using suitably designed “additional” coils. Since the feeding currents in coils for shape and position control are time-varying, also correction currents waveform must be optimized to achieve best performance. In this paper, the optimization of shape and power supply waveforms of such additional coils is tackled, with reference to FAST Tokamak

A method for the computation of magnetostatic fields in presence of magnetic materials using closed formulas, implemented on GPU architectures, is proposed. The magnetic material is first decomposed into subdomains with suited shapes, the magnetization map is then computed, and finally magnetic field is evaluated. To solve the non linear mutual interactions among subdomains, an iterative process is requested. Thanks to the availability of semi-analytical expressions, strong computational reductions can be achieved.

This paper investigates the electrical performance of innovative carbon-based nano-interconnects made by carbon nanotubes and graphene nanoribbons. The electronic transport in the carbon materials is modeled in the frame of the Transmission Line theory, where the classical per-unit-length circuital parameters are corrected by new terms arising from the quantistic nature of the transport. These parameters are related to the number of the conducting channels and the mean free path, which in turn, are expressed as functions of temperature and size. By coupling this model to the heat equation, a simple electro-thermal model is derived. Case-studies are carried out with reference to 22-nm technology node applications. Copyright ?????? 2013 John Wiley & Sons, Ltd. Copyright ?????? 2013 John Wiley & Sons, Ltd.

Inclusion of planar layered media Green's Functions (GFs) is a major issue in the computational efficiency of full-wave models derived from integral formulations. These GFs may be decomposed into quasi-dynamic and dynamic terms. In a wide range of practical applications, the quasi-dynamic terms may be given in closed form. This paper proposes two criteria to establish when the complete GFs may be approximated by the quasi-dynamic terms. These criteria are based on simple relations between frequency, line length, dielectric thickness and permittivity. If these criteria are satisfied, the inclusion of the GFs into full-wave integral models is straightforward and the overall computational cost is strongly reduced. The proposed criteria are verified through a benchmark test case. The model is then used to perform a full-wave analysis of the power lost in a microstrip, as a consequence of the excitation of parasitic modes, such as surface and leaky waves.

"The tolerance analysis of electromagnetic devices. can be tackled by using sensitivity arrays, i.e. collecting the first. order partial derivatives of a suitable performance function with. respect to design parameters. When the performance function is. expressed in terms of electromagnetic field quantities, advantage. can be taken from the splitting of derivatives involved in. sensitivity computation into a “geometric” and a. “electromagnetic” part. The paper will provide formulation for. this splitting, and some examples of application."

Carbon nanotubes (CNTs) are recently discovered materials made by rolled sheets of graphene of diameters of the order of nm and lengths up to mm. CNTs have been proposed as emerging materials able to give solutions to many of the problems given by the tight requirements of the technologies nodes below 22 nm. Presently, CNTs are considered for a large variety of micro and nano-electronics applications, like nano-interconnects, nano-packages, nano-transistors, nano-passives, and nano-antennas. Given these perspectives, many efforts have been made in literature to derive models able to describe the electrical propagation along carbon nanotubes. The electromagnetic response of carbon nanotubes has been widely examined in frequency ranges from microwave to the visible, taking properly into account the graphene crystalline. For each carbon atom in the graphene only one out of the four valence electrons (the electron) contributes to the conduction phenomenon, hence in order to model the electromagnetic response of carbon nanotubes there is the need to describe the interaction of the electrons with the electromagnetic fields produced by the electrons themselves and by the external sources, under the action of the electric field generated by the fixed positive ions of the lattice. This requires, in principle, a quantum mechanical approach, since the electrical behavior of the electrons depends strongly on the interaction with the positive ion lattice. A quantum-mechanical approach has been for instance used in, where the model is derived by using numerical simulations based on first principles. Alternatively, phenomenological approaches are possible like those based on the Luttinger liquid theory. Another possible way is given by semi-classical approaches, based on simplified models that yield approximated but analytically tractable results. Among these models, the fluid ones play a central role in CNTs modeling; in fact, despite their simplicity and immediate physically intuition, they are able to describe the main physical processes arising on characteristic lengths involving many unit cells, such as the collective effects. These models assume that the electric fields due to the collective motion of the electrons themselves and to the external sources are smaller than the atomic crystal field and also slowly varying on atomic length and time scales. In these conditions the lectrons behave as “quasi-classical particles” and the equations governing their dynamics are the classical equations of motion, provided that the electron mass is replaced by an “effective mass”, which endows the interaction with the positive ion lattice. Section 2 presents an electrodynamical model of the propagation along carbon nanotubes, derived by using the above semi-classical fluid description. The model is here presented to any type of CNTs, both metallic and semiconducting, with any chirality. The model introduces the concept of “equivalent number of conducting channels”, which represents a measure of the number of subbands in the neighbors of the nanotube Fermi level that effectively contribute to the electric conduction. This number depends on the chirality, the radius and the temperature of the CNT. Section 3 provides an example of applications of CNTs as electromagnetic material. The problem of the evaluation of the scattering characteristics of a CNT antenna is presented. An electromagnetic model is derived and discussed, based on the description provided in Section 2. Finally, in Section 4 a circuit model is derived, able to describe the behavior of CNT interconnects in the frame of the classical transmission line theory. The model describes either single or bundled CNTs. An application of CNTs as materials for innovative nanopackaging interconnect is discussed and comparisons with conventional copper technology is provided.