Operation and characterization of a plasma-filled focusing cell for radiographic paraxial diodes

Traditionally, paraxial diodes for intense, high brightness, X-ray radiography have utilized a gas-filled cell for electron beam focusing. The spot size for beams produced from such diodes is limited by the decay of the plasma return current, which causes the minimum beam spot location to drift upstream from the converter. Recent simulations using the LSP code have suggested that this drift can be minimized by using a preionized plasma-fill of density 1016 cm
^-3
instead of neutral gas. This paper describes experiments underway at Sandia National Laboratories to develop and characterize a highly ionized plasma focusing cell for the paraxial diode on the RITS-3 accelerator.