Development of the Antares Electron Gun

Antares is the Los Alamos National Laboratory 40 kJ, 1 ns, CO2 laser system, now operational. This laser system was developed for the Inertial Confinement Fusion (ICF) program and is being used for target experiments. The distributed circuit modeling, design, and operation of the large electron gun developed for the final laser power amplifier are reviewed. This gun is significant because of the large electron current area, 9 m2; the number of emitter blades, 48; the dual cathode current return; the coaxial geometry and grid control. Electron current density measurements of individual windows and over the entire length of the gun are presented. The gun components and their development are discussed. These include the emitter blades, the Kapton® /aluminum electron transmission windows (to provide an interface between gun vacuum and laser gas), the grid resistor and coaxial grid (to adjust and maintain constant electron current during the 5 ¿s pulse), the bonded stacked-ring insulator (to provide 500 kV hold-off for the grid and cathode), and the 15 m3 vacuum shell (operated at 1.3x1O-4 Pa). A unique pressure diagnostic used in the gun conditioning process is also discussed.