Electron Cyclotron Resonance (E.C.R.) Multiply Charged Ion Sources

Abstract

High charge state ions can be produced by electron bombardment inside targets when the target electron density n (cm-3) multiplied by the ion transit time through the target τ (sec) is : nτ > 5×109cm-3sec. The relative velocity between electrons and ions determines the balance between stripping and capture, i.e. the final ion charge state. (In a stripper foil fast ions interact with slow electrons involving typically n ~ 1024cm-3, τ ~ 10-14sec). In the E.C.R. source a cold ion plasma created in a first stage diffuses slowly through a second stage containing a hot E.C.R. plasma with n > 3×1011cm-3 and τ > 10-2sec. Continuous beams of several μA of C6+, N7+, Ne9+, A11+ are extracted from the second stage with normalized emittances of ~ 0.57π mm mrad. The absence of cathodes and plasma arcs makes the source very robust, reliable and well-fitted for cyclotron injection. A superconducting source is under development.