LEVIS active anode lithium ion source development on PBFA-II

Summary form only given. Experiments are ongoing on the PBFA-II accelerator to optimize an active lithium ion source in a 15-cm focusing applied-B ion diode using the LEVIS (Laser Evaporation Ion Source) process. Spectroscopic observations indicate the presence of a preformed anode plasma prior to the power pulse. However, the time between application of high voltage and the initiation of significant ion current on the LEVIS diode is roughly comparable to that seen with a passive diode using LiF as the ion source. This is consistent with time-dependent diode modeling, which shows that both LEVIS and LiF are achieving enhanced diode current within a few nsec of the expected time determined from ideal diode theory. The LEVIS-generated beam has attained focal spot sizes of 6-8 mm (horizontal focusing), comparable to that seen with the LiF source operated with similar parameters. There are preliminary indications that diodes with the LEVIS source experience less impedance decay for comparable ion beam currents than those with the LiF source.