HiPER target studies: towards the design of high gain, robust, scalable direct-drive targets with advanced ignition schemes

An essential element of the HiPER project is the design of high gain targets, compatible with high repetition-rate operation and that can be mass produced at low cost. HiPER WP9 (Work Package 9 Requirements analysis for the fusion programme) studied schemes based on direct laser irradiation and advanced ignition (fast ignition and shock ignition), which have potentials for gain in excess of 100 at laser energy of about 1 MJ. To begin with, a very simple target was designed, which could allow for ignition demonstration with a few hundred kJ laser, and can be scaled at higher energy and gain. The ignition requirements have been determined, and crucial issues have been identified. This led to select shock ignition as the main option, since it turns out that all the relevant issues could be tested experimentally at existing facilities in the present decade. WP9 investigated irradiation schemes, target symmetry and stability issues, sensitivity to parameter changes, requirements for beam delivery and focusing and target positioning. Current work is directed towards increasing target robustness, scaling to greater energy, and designing targets for full scale demonstration.