Characterizatin of LEVIS (laser evaporation ion source) for light ion inertial confiement fusion

LEVIS (Laser EVaporation lon Source) [1] is being developed as an active ion source for intense applied-B ion diodes in the light ion fusion program at Sandia. This technique uses either a dye laser (670.8 nm, 1 μs), an Nd:YAG laser (1.06 μ, 8 ns), or some combination of the two to evaporate lithium from various thin-film/substrate combinations. This source has been fielded on ion diodes on both the SABRE and PBFAII accelerators. Rapid impedance collapse, low voltages, and protons in the accelerated beam from those accelerators imply surface contamination, and points out the need for pre-shot cleaning of some kind. DC current, pulsed current, and glow discharge heating methods are being evaluated in light lab experiments as means of cleaning the thin-films in-situ. Diagnostics which are being fielded include a quadrupole mass spectrometer, a laser deflection method sensitive to refractive index gradients [2], and optical spectroscopy. This light lab work is a continuation of that described in [2].