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TOPICA is an innovative tool for the simulation of the Ion Cyclotron Radio Frequency (ICRF) antenna systems that incorporates commercial-grade graphic interfaces into a fully 3D self-consistent description of the antenna geometry and an accurate description of the plasma; it can be considered as a "Virtual Prototyping Laboratory" to assist the detailed design phase of the antenna system. Recent theoretical and computational advances of the TOPICA code has allowed to incorporate a CAD drawing capability of the antenna geometry, with fully 3D geometrical modeling, and to combine it with a 1D accurate plasma description that takes into account density and temperature profiles, and FLR effects; the profiles are inserted directly from measured data (when available), or specified analytically by the user. The coaxial feeding line is modeled as such; computation and visualization of relevant parameters (input scattering parameters, current and field distributions, etc.) complete the suite. The approach to the problem is based on an integral-equation formulation for the self-consistent evaluation of the current distribution on the conductors. The environment has been subdivided in two coupled region: the plasma region and the vacuum region. The two problems are linked self-consistently by representing the field continuity in terms of equivalent (unknown) sources. In the vacuum region all the calculations are executed in the spatial (configuration) domain, and this allows triangular-facet description of the arbitrarily shaped conductors and associated currents; in the plasma region a spectral representation of the fields is used, which allows to enter the plasma effect via a surface impedance matrix; for this reason any plasma model can be used, and at present the FELICE code has been adopted; special techniques have been adopted to increase the numerical efficiency. The TOPICA suite has been previously tested against assessed codes and against measurements of mock-ups and existing antennas. This work is devoted to an extensive set of comparisons between measured and simulated reflection coefficients (magnitude and phase), both in vacuum and with plasma during ALCATOR C-MOD operation. The comparison demonstrates a very good agreement, leading to a validation of TOPICA as a predictive tool.

TOPICA (Torino Polytechnic Ion Cyclotron Antenna) code is an innovative tool for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF) antennas, i.e. accounting for realistic 3D antenna geometries and for accurate 1D plasma models. The tool calculates the antenna input parameters at the feeding ports given the exact port excitation. Moreover, it calculates the current distribution and electric field maps wherever specified. The recent upgraded parallelized version of TOPICA permits the analysis of large and complex antenna structures in a reasonable simulation time (less than one day). A detailed analysis of the performances of two ITER ICRF antenna geometries has been carried out, underlining the strong dependence and the asymmetries of the antenna input parameters due to plasma conditions. An optimization of the antenna dimensions has also been accomplished. Electric current distribution on conductors in the vacuum region and electric field distribution in the vacuum region and at the interface with plasma edge have been calculated as well. The analysis shows the strong capabilities of the parallelized TOPICA code as a predictive tool and its usefulness to ICRF antennas final design.

In the past twenty years plasma-based propulsion systems have found increasing aerospace interest; although they were initially conceived as rockets for interplanetary missions, more recent advances in plasma-based concepts have led to the identification of radio-frequency (RF) generation and acceleration systems as capable of providing not only continuous thrust, but also controllable exhaust velocities, as required in maneuvering applications. The most interesting such studies for plasma propulsion are those focused on the possibility of coupling radio frequency power to plasma, exploiting the possibility of having very efficient devices to generate and heat the plasma, magnetically confining it in a trap in the heating region, so that ion can escape the magnetic trap only when they are energetic enough to be converted into direct out-going flow which provides the thrust. The structure of this system is therefore based on of three stages where plasma is respectively generated, heated and expanded in a magnetic nozzle. The heating stage acts as an amplifier; here plasma is heated by the radio frequency waves by the process of ion cyclotron resonance. It has been developed and tested a numerical tool for the electromagnetic modeling of the ICRF antenna, of the RF booster unit of plasma thrusters, and of the RF-plasma interactions. The latter is studied in the critical ICRF acceleration region by setting up a convenient Electromagnetic (EM) analytical and numerical model based on the Moment-Method solution of a suitable set of integral equations. Solution of the relevant integral equation directly provides the electric surface current density induced on antenna conductors, but the ultimate quantity to be computed is the circuit characterization (e.g. admittance matrix) at the input ports. ©2005 American Institute of Physics