Gas pre-ionization system for DECADE Module 2 PRS experiments

DECADE Module 2 (DM2) implodes argon gas-puffs in 200-300 ns from initial radii of 2.5-5 cm to generate K-line radiation. An important issue for these experiments is the lower-than-expected K-line radiation associated with such large radius implosions. Preionization may improve the implosion quality by improving the symmetry of the initial current flow. A preionizer is described based on photoionization by ultraviolet (UV) illumination from a flashover source. The preionization is diagnosed using a high-sensitivity interferometer. This UV source produces 1-10% ionization of the outer periphery of the argon gas distribution prior to the arrival of the flashboard plasma. DM2 experiments indicate increased, more reproducible K-shell yields when this preionization system is incorporated.