Fuel target production for HiPER presents unique challenges to both industrial and scientific communities. Laser targets of this complexity and precision are currently produced at approximately one per day. Operating at 10Hz, HiPER will need a daily minimum of 864,000 targets. Allowing for wastage and defects, each Laser Energy plant can be expected to require nearly a million per day.
Achievements in modern mass-production of complex objects (such as cars) make the implied increase in required production rate seem less daunting than would otherwise be the case.
HiPER target designs are likely to be spherical, consisting of a glow discharge polymer shell or of foam. Targets will be filled with Deuterium and Tritium at cryogenic temperatures (approximately 14K (-259°C)). The target’s surface will have a heat shield to protect it from the reactor environment while in flight from injector to chamber centre.
After fuelling, targets are held in a tightly controlled isothermal environment. After layering with a thin ice coating on the internal surface of the shell, each target is then injected into the reactor where its heat shield protects it for the short period of time before it reaches the centre of the reactor where it is engaged by the lasers.
Shell production techniques include wet chemistry, dielectrophoretics and wafer based production. Unprotected shell targets can be filled using diffusion, as deuterium and tritium are very small molecules and can pass through the GDP shell over time. Foam targets may be filled by wicking, a process similar to that of a candle drawing fuel to its flame. Filling of protectively coated targets of either shell or foam type has yet to be assessed. It may also be possible to use wafer based production techniques (micro electrical mechanical systems and micro-fluidics) to produce a target in its finalised form.
Current mass production techniques must be improved upon and new approaches explored to achieve target mass-production for a Laser Energy plant. Those most appropriate for the optimised target design can then be selected and integrated into a production line.
Target metrology will also need to be automated.
Significant challenges exist, but studies predict that solutions to the target mass production challenge can be achieved within ten years.