Plasma-filled focusing cells for paraxial diodes on RITS-3

Abstract

Summary form only given. Traditionally, the paraxial radiographic diode has relied on a gas-filled chamber to focus an electron beam into a small spot for the purpose of generating X-rays. Focusing is provided by the electron beam-produced plasma whose density increases during the course of the beam pulse. Simulations using Lsp, a particle-in-cell code, have shown that the location of the electron beam focus wanders during the timescale of the pulse in this case, resulting in a larger radiographic spot than is desirable. Lsp simulations have also shown that replacing the gas-filled focusing chamber with a fully-ionized plasma of density on the order of 10/sup 16/ cm/sup -3/ will prevent the spot from significantly wandering, hence resulting in a smaller, more stable spot size. Sandia National Laboratories is implementing a plasma prefilled paraxial diode on the RITS-3 accelerator. The plasma-filled cell will be created using a z-discharge in a hydrogen fill. Laser interferometry is used to assess the plasma density on bench-top experiments, and plans are underway to perform the diagnostics during RITS-3 experiments. Details of the plasma source, its characterization in a bench-top setting, and plans for investigation during RITS-3 operation are presented.