Return-Current Heating and Implosion of Cylindrical CO2-Laser-Driven Targets

The Helios laser system has been used to deliver 2.3 kJ to the capped end of 0.75-mm-long, 130-μm-diam hollow rods of 5-μm wall thickness. Soft-x-ray pinhole pictures demonstrate the cylindrical implosion of these targets. The measured 130-eV core temperatures from the filtered pictures and the 7×${10}^6$-cm/s collapse velocity from optical streak photographs are consistent with heating by a 0.8×${10}^6$-A return current, representing the recycling of 15% of the hot-electron emission.