Cut-away view of MiniECR source.

Both electromagnet and permanent magnet ECR sources tend to be rather large and complex. Such bulk is undesirable for industrial accelerator systems designed to produce radioactive isotopes, for portable accelerators, or for proton therapy. Reducing the size and complexity of ECR sources for accelerator applications would have a significant impact on these facilities. Before now, the size of the plasma chamber was limited to dimensions larger than the rf wavelength. Scientific Solutions designed and patented a miniature ECR source whose dimensions are no longer restricted by the rf wavelength. Judicious use of dielectric materials allows the dimensions of the plasma chamber to be independent of the rf wavelength and can be made almost arbitrarily small.

The rf power required to produce a plasma is proportional to the plasma volume. Therefore reducing the plasma volume reduces the rf power required to sustain that plasma. Since most of the cost of an ECR source is in the rf system, a significant reduction in rf power translates directly into a significant reduction in the overall cost-particularly if multi-kW klystrons can be replaced with solid-state rf amplifiers operating below the 1 kW level.

A secondary benefit of this approach is the dielectrics concentrate the rf electric field in the plasma region of the chamber. RF voltage enhancement factors of three or more are possible depending on the details of the plasma chamber. This enhancement factor ensures rapid initiation of the plasma even at low rf power levels (a factor of three enhancement increases the rf voltage to a level equivalent to nine times higher rf power). The dielectric walls of the plasma chamber also help confine the ions in the plasma. This confinement enhances the efficiency and therefore the extracted ion current. The MiniECR source is a cylinder 10 cm diameter by 10 cm long (not counting the waveguide).