Beam transport and focusing on PBFA II

Summary Form only given, as follows. Ion beam transport and focusing experiments on PBFA II (Particle Beam Fusion Accelerator II) are continuing to improve both the total energy transported to the axis and the peak power density measured on axis. A varied set of on- and off-axis diagnostics includes an on-axis ion pinhole camera, magnetic spectrograph, off-axis K alpha soft X-ray cameras, Faraday cups, and witness plates. Diagnostics, transport theory, and simulations indicate that the total energy on axis is limited by excessive vertical focusing by the applied and self-fields. At present, the beam divergence is limiting the on-axis horizontal FWHM to 5.5 mm for high-power experiments. Experiments to determine the scaling and source of this divergence are continuing. The accelerator is now being operated reliably at the 3/4 energy level into an ion diode. At 3/4 energy, the diode consistently couples 700 kJ of energy into the diode, with over 500 kJ of ion energy delivered to the transport system. Over 120 kJ of proton energy has been transported inside a 1-cm radius.<>