G. Pollicino

TWT magnetic focusing structure optimization by parallel evolutionary algorithm

Purpose – The purpose of this paper is to present the application of a novel hybrid algorithm, called MeTEO (Metric‐Topological‐Evolutionary‐Optimization), based on the combination of three heuristics inspired by artificial life to the solution of optimization problems of a real electronic vacuum device.Design/methodology/approach – The Particle Swarm Optimization (PSO), the Flock‐of‐Starlings Optimization (FSO) and the Bacterial Chemotaxis Algorithm (BCA) were adapted to implement a novel meta‐heuristic MeTEO the FSO has been powerfully employed for exploring the whole space of solutions, whereas the PSO is used to explore local regions where FSO had found solutions, and BCA to refine the solutions found by PSO, thanks its better performances in local search.Findings – The optimization of the focusing magnetic field of a Travelling Wave Tubes (TWT) collector is presented in order to show the effectiveness of MeTEO, in combination with COLLGUN FE simulator and equivalent source representation. The optimiz...

3-D Finite Element Analysis of TWT grid electron guns

A novel three-dimensional FE procedure for the analysis of electron guns inside traveling wave tubes (TWTs) is presented, illustrating its main features. In this procedure, electron trajectories modeling cathode emission are obtained by solving a Vlasov-Poisson system of equations together with the relativistic dynamical equations of motion, under consistent particle injection conditions. This coupled electromechanical problem is solved iteratively by assuming stationary conditions. Simulation results concerning a gridded electron gun are presented, showing good agreement with available experimental data

An FE Tool for the Electromagnetic Analysis of Slow-Wave Helicoidal Structures in Traveling Wave Tubes

In this paper, the authors present a 3-D dedicated finite-element tool expressly conceived for the analysis of traveling wave tool helicoidal slow wave structures (SWSs). Accurate analysis of the SWS is a difficult task due to its complex geometry. Moreover, in order to achieve the design parameters a specific post-processing is required. Consequently, specialized 3-D numerical simulators are needed to carry out the design process. The developed tool includes a dedicated mesh generator, an eigenmode and a driven mode solver, and a post-processing module. An example of a typical SWS analysis performed by using the tool is also given

A New Self-Consistent Unbounded Magnetic Field 3-D FE Computation for Electron Guns

An innovative 3-D Finite Element approach for the computation of the self-consistent unbounded magnetic field of electron beams is presented for the analysis of electron guns. The solution of the whole problem is obtained by solving iteratively a Vlasov-Maxwell equation assuming stationary conditions together with the relativistic dynamical equations of motion. The self-consistent unbounded magnetostatic field is computed by using an edge elements curl-curl formulation for the magnetic vector potential. A fictitious boundary iterative algorithm is adopted to overcome the problem of boundary conditions assignment. An accuracy test concerning the spread of a relativistic beam and the simulation of a complex gridded electron gun are shown in order to validate and better illustrate the procedure.

Finite Element Electromagnetic Analysis of TWT Slow-Wave Structures in Grid Environment

In this paper, some new finite element procedures are presented to analyze TWT helix slow-wave structures in a distributed computing environment. In particular, very computing time expensive analyses required in TWT SWS simulations are parallelized in order to obtain a remarkable reduction of computing time. The example presented regards the construction of the Brillouin diagram of a helix SWS. The obtained results confirmed us the good performance of the grid environment for the numerical analysis and optimization of TWTs.

GRID-Based Prediction of Electromagnetic Fields in Urban Environment

In this paper, a grid-based 3D ray tracing procedure is presented for the prediction of electromagnetic field in urban environment in the presence of multipaths, reflections and diffractions. In the procedure, electromagnetic field strength is obtained by all the contributions originated, evaluated by exploiting the ray tracing method in grid environment. The obtained results have shown the good performance of the grid environment for the prediction leading to reduction of one-order of magnitude of the computing time.

A 3-D Finite Element Poisson–Nernst–Planck Model for the Analysis of Ion Transport Across Ionic Channels

A 3-D finite element steady-state Poisson-Nernst-Planck model is presented and applied to the analysis of the ion transport across ionic channels of cellular membrane. The model allows us to obtain an accurate description of ion flow across the cell membrane. An example of application to the case of a K channel is also illustrated. The resulting current-voltage curve for the K channel shows excellent agreement with experimental measurements

3-D FE Particle Based Model of Ion Transport Across Ionic Channels

In this paper a novel 3-D Finite Element (FE) particle based approach is presented to investigate the ion flow across ionic channels. This consistent model foresees direct integration of the dynamical equations of ions subject to electromagnetic forces inside membrane channels, considering ion-ion interactions and taking into account explicitly the effects of molecular friction and thermal noise. The simulation results presented show that the mechanism of opening and closing of the membrane channels (Ca) as a function of the membrane voltage can be correctly reproduced by a particle model.

FE analysis of magnetic shielding screens based on mortars containing ferromagnetic particles

This paper documents the research towards the development of a simple approach to model composite magnetic materials through Finite Elements Method analysis. The computational problems found in representing composite materials at microscopic level are solved through a homogenization technique based on energy balance. The technique was used to estimate the effective permeability of a material, and through a larger scale simulation, its shielding effectiveness against extremely low frequency magnetic fields. The results were then validated using an experimental setup.

Effective permeability of shielding mortars containing ferromagnetic particles by using FEM

This paper proposes a strategy for the evaluation of effective permeability of mortars containing ferromagnetic particles for magnetic shielding. The representation of the composite mixture is done by using just 3-D inclusions in a finite element method. A statistical analysis is then performed on thousands of meshes representing the same sample geometry, with different inclusions distribution. Homogenization technique based on energy balance is then adopted in order to compute the effective permeability of the mortars. Thus, we are able to establish a relationship between the components of the mixture and an ideal equivalent homogeneous magnetic material with an assigned magnetic effective permeability. The results has been verified by using experimental data.