LiF ion source performance on PBFA II

Recent LiF ion source experiments have been conducted on Sandia National Laboratories' Particle Beam Fusion Accelerator (PBFA) II. This facility is designed to provide a 30 MV, 100 TW power pulse to an applied B ion diode to investigate the suitability of light ions for inertial confinement fusion (ICF). Singly-ionized lithium is the desired ion species for these experiments because it has the proper range in target materials at 30 MV. LiF-coated anodes have been shown in experiments on other accelerators to produce relatively pure (>70%) Li+ beams. Earlier PBFA II experiments using porous anodes coated with LiF confirmed Li+ production from LiF films. The present PBFA II experiments use 0.6 μm films of LiF evaporated onto a stainless steel anode surface to provide a 1 MA, 25 ns FWHM pulse of Li+ ions at energies of 6--9 MeV. The physical mechanism for production of ions from thin films of LiF has not previously been identified. One of us, T. Green, has developed a model which is consistent with LiF data from PBFA II and laboratory experiments and may provide a framework for understanding Li+ ion production from thin LiF films in an applied B diode