Driver beams must hit targets accurately in an inertial fusion energy power plant. Current requirements are less than ±200 μm for indirect drive targets and ±20 μm for direct drive targets. A recent target tracking and position prediction experiment was carried out using indirect drive target sized projectiles.1 The results of that scaled experiment extrapolate to a standard deviation of 220 μm error in position prediction at power plant size. Greater accuracy will be required, especially for direct drive targets. Greater standoff between the detectors and the targets (previously about 3 cm) will also be required to allow for detector shielding. Diffraction effects are expected to be more important with greater standoff and accuracy requirements.

An improved optical target tracking and position prediction system is being designed, as part of the Target Injection and Tracking Experiment at General Atomics, to achieve the above requirements. Concepts for improving accuracy include the use of multiple photodiode arrays, a temperature controlled environment, vibration-limiting detector mounts, additional detector stations, improved electronic noise suppression, and constant-brightness laser light sources. The current status of this design work is presented.