Conceptual Design of a Sputter-type Negative Ion Source Based on Electron Cyclotron Resonance Plasma Heating

A design for a negative ion source based on electron cyclotron resonance plasma heating and ionization by surface sputtering is presented. The plasma chamber of the source is an rf-cavity designed for TE111 eigenmode at 2.45 GHz. The desired mode is excited with a loop antenna. The ionization process takes place on a cesiated surface of a biased converter electrode (cathode). The ion beam is further “self-extracted” through the plasma region. The magnetic field of the source is optimized for both, plasma generation by electron cyclotron resonance heating, and beam extraction. The source can be used for a production of a variety of negative ions ranging from hydrogen to heavy ions. The potential users for the source concept range from large scale accelerator facilities, utilizing H ion beams, to dc tandem accelerators for heavy ions. The benefits of the source concept compared to widely used filamentand inductively coupled rf-driven sputter-type sources are the lack of consumable parts and low neutral pressure minimizing the stripping losses of negative ions. In this article we will focus on the H production scenarios with the novel source. The benefits and drawbacks of higher frequency operations are also discussed.