Light ion fusion research in the United States

Power concentration has been the principal concern for Inertial Confinement Fusion (ICF) with light ion beams. Recently a proof-of-principle experiment on ion beam focusing has been completed on Proto I and indicates the Particle Beam Fusion Accelerator II (PBFA-II) beam should be focusable for high intensity targets to study ignition. The results are being scaled to PBFA I now. The theoretical stability of the electron sheath in the diode has been examined, and the growth rates are typically 5% of the electron cyclotron frequency. A new spectroscopic diagnostic has been developed to measure the electric fields and ion velocity distributions in the diode. Recent experiments with glow-discharge cleaning have shown that the ion species can be controlled, and the purity can be improved substantially. Plasma erosion opening switches will compress the power pulse to match the target acceptance time on PBFA II. Experiments with these switches on single module accelerators show power gain. Currents of 5 MA have been interrupted in 20 ns in other experiments. The high voltage lithium ion option has been chosen for PBFA II, and the Applied-B diode has been selected as the first diode for the first shot on PBFA II in January 1986