Expectations for the National Spherical Torus Experiment's high harmonic fast wave system

High harmonic fast waves (HHFW) have been chosen as the primary method to d rive steady state currents in the National Spherical Torus Experiment (NSTX ). The somewhat limited experience with this frequency range in conventiona l tokamak plasma indicates that the coupling to electrons should be success ful; however, there is no experimental data base for HHFWs in the unique an d rapidly varying plasma regimes expected for NSTX. In this paper, we descr ibe how the HHFW antenna was designed for NSTX using the computer codes to help make decisions that might affect the system's performance and operatio n. The antenna geometry has been optimized to maintain the power handling a nd phase control requirements within engineering constraints. The physics i ssues that lead to the choice of poloidal current strap orientation are dis cussed. Expectations for current profile control using the antenna's phase control system are also discussed.