Transportation of a pulsed ion beam formed by a self-magnetically insulated diode

Summary form only given. We present the results of a study on transportation of a gigawatt power pulsed ion beam formed by a self-magnetically insulated diode with an explosive-emission graphite cathode. Studies were performed using diodes of different design: a strip planar and focusing diode, and a spiral diode, all operated in double-pulse formation mode with the first negative pulse (300-500 ns, 100-150 kV), followed by the second positive pulse (150 ns, 250-300 kV). For increasing ion beam focusing efficiency and preventing the ion loss from the beam volume during propagation to the target, we used a metal shield installed on the grounded electrode. The shield was made from 1 mm stainless steel foil. We observed that the beam diameter at the focus decreases from 60 mm (without shield) to 40-42 mm (with a shield) which leads to an increase in the energy density by a factor of 1.5-2 being 4-5 J/cm² at the focus. Use of the shield on the grounded electrode provides decrease in the half-angle beam divergence from 11° to 7.5-8°¹. The effectiveness of the metal shield we attribute to both the elimination of magnetic filed in the beam transport region and realization of the transverse neutralization mechanism. Additional studies using a pin hole camera and heat sensitive paper for beam imprinting at the target showed that the divergence angle of the beam propagating inside the shield does not exceed 3°.