Improved virtual cathode formation in Inertial Electrostatic Confinement

Summary form only given. Continued experimentation on the inertial electrostatic confinement (IEC) of ions in a virtual cathode potential well at Los Alamos National Laboratory (LANL) is presented. The IEC virtual cathode is formed by focusing six diametrically opposed electron beams to the center of a spherical vacuum chamber. The electrons are accelerated using two highly transparent, concentric spherical grids held at positive potential. The converging electron beams generate a parabolic potential well inside of the innermost grid, which is measured using a tungsten filament emissive probe. Ions created inside of the virtual cathode will remain trapped, with the maximum ion energy determined by the well depth. Recent upgrades to the LANL IEC device have produced virtual cathode well depths greater than 60% of the applied grid voltage. These upgrades include: modified , a new 13 kV Marx bank pulsed power supply, and an improved gas injection system. Continued experiments will increase the applied voltages further into the fusion-relevant regime to study the feasibility of a net gain IEC fusion reactor. Additionally, previous experiments at LANL have confirmed the so called (POPS): a resonant, phase-locked radial oscillation of the IEC plasma induced by applying an ion-specific RF driving frequency to the innermost grid. The implementation of POPS oscillations has been observed to extend the lifetime of the virtual cathode potential well. This extended lifetime is likely due to the resonant heating and eventual ejection of trapped ions that degrade the virtual cathode. The most recent experimental POPS data will be presented along with plans for future POPS experiments.