SOURCES OF MULTIPLY CHARGED IONS FOR HEAVY-ION FUSION

We report experiments on methods to raise the proportion of multiply charged ions for high-flux-ion extraction from vacuum-arc plasma sources. Beams of doubly and triply charged ions have application to induction linacs for heavy-ion fusion. We confirmed that the arc cathode material strongly influenced the ion-charge-state proportions. We believe the electrostatic potential of the plasma streaming from the arc played a major role in the transport of multiply charged ions. Reduction of electron losses from the plasma increased the observed fluxes of doubly charged ions. We inhibited electron loss and enhanced the flux of multiply charge ions by applying a bias voltage to the plasma source and by adding an axial magnetic field. We also investigated a method to increase the proportion of multiply charged ions by time-of-flight separation following rapid switching of the expanding plasma. We developed a new arc-source geometry for the experiments. The source had a hollow anode and an axial magnetic field to anchor the position of emission spots on the cathode.