Feed Optimization For the Slotted Line Antenna For High-Density Plasma Production

Investigations on the optimization of feed structures for exciting the slotted line antenna for high-density plasma production are presented. Each feed structure used (except the direct feed) excites a preferred component of the wave electric/magnetic field. It is seen that the efficacy of plasma production using the different feeds depends directly on the relative importance of the field components (which the feeds excite) for the slow wave mode of the antenna. The optimal feed is shown to be a dipole antenna, oriented so as to excite the radial component of the electric field within the slotted line structure. The plasma characterization results as a function of the input microwave power and the magnetic field in the antenna region are also presented and discussed. The ability of the antenna to maintain high-density plasmas well away from electron-cyclotron resonance is demonstrated.