Targets injected into the chamber must be tracked in flight with very high accuracy. When a target has been acquired by the tracking system, an estimated prediction is made of its position at closest point of travel to reactor centre. This information is passed to the target engagement system which determines the corrections needed for positioning and timing so that the lasers can engage the target effectively at that point.
The tracking systems must accurately locate target position within the chamber, but must also operate reliably and accurately within the chamber environment – 700°C, high radiation, medium vacuum (10-3mBar(a)) and the chamber potentially retaining some residue from the previous fusion burst.
Protecting the tracking system from the fusion burst is not feasible as tracking needs to be continuous up to point of laser engagement. The system must therefore be designed to withstand the fusion burst including any resulting electromagnetic, radiation and neutron emissions.
The tracking system is likely to incorporate two or more different technologies to minimise the effect on its accuracy of any fusion event and to obviate any residual effects.
Military based solutions for the tracking requirement already exist with the capability to measure position to within a factor of ten of the requirement for HiPER. With ten years of development planned before selection of this technology, a number of prototype systems are likely to be built before the final approach is decided upon.