METHODS OF CALCULATING SELECTED GEOMETRICAL EFFECTS IN THE DESIGN OF ICRH ANTENNAS

This paper discusses the effects of realistic antenna geometry on the design and performance of ion cyclotron resonance heating (ICRH) anten nas and presents methods to calculate these effects and to modify perf ormance predictions that are based on idealized antenna geometry. It e mphasizes the engineering aspects of antenna design, such as the elect rical characterization of the antenna for inclusion into the power dis tribution network, as well as detailed analysis of the Faraday shield structure. The analysis of the Faraday shield includes the calculation of the shield's power transmission and dissipation properties (rf loa d), its effect on the strap phase velocity and characteristic impedanc e, and the rf heat distribution for the purpose of thermal analysis. T he finite antenna length and its interaction with the recessed cavity and reduced phase velocity are presented in terms of an effective ante nna length. Calculation of interstrap coupling with slotted septa sepa rating the straps is presented, including a discussion of the basic tr ade-offs between directionality, loading, and circuit stability in the case of directional phased arrays for fast wave current drive at ICRH frequencies.