Target injection and tracking for inertial fusion energy

In an inertial fusion power plant, several cryogenic targets must be injected each second into a reaction chamber with speeds of about 100 m s−1. This speed can be achieved with an acceleration in the range from 1000 to 10 000 m s−1. The total accuracy of driver beam pointing and target position prediction must be less than ±0.6 mm for a 3 mm beam spot radius. A 0.1 μm thick dual membrane supporting the capsule in the hohiraum will allow nearly 2000 m s−2 Z acceleration. The strength of frozen DT in the capsule is calculated to allow acceleration in excess of 10 000 m s−2 if the DT temperature is less than 17 K. A gas gun is the preferred device for injecting indirect drive targets owing to its simplicity and proven reliability. The amount of gas required for each target (about 10–100 mg) is acceptable. A revolver loading mechanism is recommendced with a cam-operated poppet valve to control the gas flow. Slots near the muzzle of the gun barrel are recommended to vent gas and thereby to improve accuracy and to aid gas pumping. Optical target tracking and electronic timing devices can predict target arrival time with sufficient accuracy. Target steering by electrostatic deflection of the in-flight target is shown to be feasible and would avoid the need to point the beams actively. Calculations show that induced tumble from electrostatically steering the target is not excessive. An experiment has been designed to develop target injection and to verify the predicted accuracy of sequential injection and tracking of multiple targets.