MAGIC calculations for a large-area microwave plasma source

Summary form only given, as follows. The MAGIC code was used to analyze a two-dimensional model of a microwave surface-ECR plasma source to obtain microwave field and electron-trajectory information for design purposes. This source uses permanent magnets to generate a cyclotron-resonance surface across the aperture of a rectangular or circular waveguide. The permanent magnets are located in channels in an aluminum grill, and are held in the channels by a ceramic waveguide/vacuum window. The grill and window act as obstacles in the waveguide. Electron-trajectory analysis is done to examine kinetic power deposition on the grill and nearby waveguide walls, and electron heating by the microwave fields in the static field generated by the permanent magnets. The field is modeled by equations that approximate the actual magnetic field. MAGIC was used to study the reflection from the grill and window, and to determine the effect of adding boron nitride inserts in the open slots of the grill to reduce the reflection coefficient. The width of the open spaces and the number of magnet rows were varied to find an optimum design. The waveguide was modeled as a parallel-plane waveguide with a 15-cm spacing. The TM/sub 1/ parallel-plane waveguide mode was launched at the input end. A tapered transition was also designed to transform from standard WR284 waveguide to the 15-cm/spl times/20 cm source waveguide. The resulting design minimized the generation of higher-order modes and reflection of the dominant mode. Reflection coefficients as low as 20% could be obtained with 47% of the waveguide aperture covered by the grill. Minimum reflection was obtained when the spaces between magnet rows were half-filled with boron nitride. A few electrons were used for single-particle trajectories, and superelectrons in a background of immobile ions were used to model an underdense plasma. The kinetic power delivered to the grill and walls was found to be relatively small.