ICRF antenna modeling and simulation. Final report

ICH is a central element in all current and planned large tokamak experiments. In addition to its potential role as a primary heating source, ICH is also useful for equilibrium profile control and sawteeth stabilization. Optimization of ICRF antenna performance for either heating or current drive depends critically on the complex balance and interplay between the plasma physics and the electromechanical system requirements. For example, antenna designs and operational modes that minimize impurity production and induced sheath formation may, however, degrade current drive efficiency. Such effects have been observed in experiments involving {pi} versus zero antenna phasing. Solutions to these kinds of technical problems -- especially important for a reactor grade antenna where survivability becomes a key issue -- require an integration of theory, numerically aided design through modeling and simulation, and experimental investigations. SAIC`s efforts in helping to formulate approaches to address the above issues have focussed on two interdependent plasma physics areas: numerical modeling and simulation of ICRF antenna performance including antenna-plasma coupling, and sheath physics in the neighborhood of antennas with emphasis upon Faraday shield and cur-rent strap sheaths. The main goals of our work are to: provide a predictive capability for evaluating antenna performance, including radiatedmore » field and power spectral distributions, plasma/antenna coupling, develop an improved understanding of sheath physics phenomenology in the vicinity of ICRF antennas, particularly in the low edge densities where 2-D effects are fundamental, and incorporate the microscopic sheath effects into the macroscopic plasma/antenna performance predictions. These goals have helped SAIC to formulate an approach to the development of a modeling and simulation environment in which the important technical questions affecting ICH can be analyzed and evaluated.« less