Performance characterization studies of a flat field volume ECR ion source

An all-permanent-magnet, 6 GHz ECR ion source with a central flat magnetic field profile has been evaluated at the Holifield Radioactive Ion Beam Facility, Oak Ridge National Laboratory. This magnetic field configuration produces a large volume ECR zone when the input RF radiation is tuned in resonance with the central flat field, thereby increasing the probability for absorption of microwave power and, consequently, the hot electron population in the plasma volume. The magnetic field of the source can also be converted from the flat-B configuration to the traditional minimum-B configuration and vice versa. The studies show that the volume ECR configuration produced higher charge states and higher intensities for high charge states than the conventional minimum-B configuration.