Development of a microwave cusp accelerator driven by electron cyclotron resonance

Summary form only given. A microwave ion source is presented that employs a plasma discharge driven by distributed electron cyclotron resonance absorption (ECR) in a magnetic field cusp geometry. Ions are accelerated out of the cusp at controllable energies by a combination of magnetic mirror forces and an applied anode voltage. Previous experiments have demonstrated the ability to create controllable potential differences in an ECR cusp plasma and induce ion beam emission. However, the axial profile of the accelerating potential has, up to this point, remained largely unmapped. As a result, the interaction of the ion production zone (where ECR occurs) and the acceleration zone (where the accelerating potential drop occurs) is not well understood. In this paper, we present detailed measurements of the plasma potential along the axial acceleration zone of the magnetic cusp as a function of absorbed microwave power, neutral gas pressure, and applied anode voltage. These potential measurements are correlated with ion energy measurements to form a coherent picture of the ion acceleration mechanism within the magnetic cusp.