Multiple Arc Ion Sources For Heavy-Ion Fusion

Heavy ion fusion requires high current density, low-emittance ion sources that are reliable and long lived. We report experimental and simulation results on the performance of carbon arc ion sources intended for use in a scaled induction linac experiment. These sources use a planar electrostatic plasma switch to prevent plasma from entering the extraction gap before the extraction voltage pulse is applied. This provides good beam optics for short pulse extraction. Measurements of current density and emittance are presented. Both double-slit and channel plate-pepper pot techniques are used for emittance measurement. Data presented are from a compact three-arc source with plasma coupling of the cathodes. Data on lifetime and multiple arc triggering are also presented. The plasma switch performance has been modeled with a 2D explicit electrostatic particle-in-cell code. Results showing plasma shutoff phenomena and behavior during extraction are presented. A 2D steady-state ion flow model is also used to predict the optimum plasma switch geometry for producing minimum emittance generation at the switch surface.