Target fabrication

The majority of targets that are made by the group have the requirement for very thin layers of metallic or plastic coatings. These are manufactured using a range of capabilities including physical vapour deposition (PVD) such as thermal and electron beam evaporation and sputtering and chemical vapour deposition (CVD). It is often the case that the manufacture process requires multi-layer or multi-element coatings which requires an understanding of multiple processing steps to ensure integration with the rest of the manufacturing process.

Target components are usually sub-mm in size and in some cases can have dimensional tolerances of a few microns and a surface roughness tolerance of a few nanometers. Using the latest in precision milling, laser micromachining and diamond turning we are able to machine a wide range of materials and geometries including hohlraums, cones, gas cells, diagnostic elements, and target support structures. Combining these processes with electroforming, thin film coating and etching enables the highest precision target to be manufactured.

To produce large numbers of targets for the next generation of high-repetition rate facilities such as EPAC and EUXFEL, it is possible to batch produce targets and target structures. Combining spin coating and lithography with Deep Reactive Ion etching, which is a highly anisotropic etch process, we can create deep, steep-sided holes and trenches in wafers/substrates, typically with high aspect ratios. Using both Bosch and Cryogenic etch processes enables us to produce smooth sidewalls or tapered features which can be tailored for the experimental need.

Materials development provides a key role in target manufacture. Research and development into novel materials including low density polymer foams and aerogels enables the group to provide targets that are of interest to the community. The ability to dope or load the materials provides contrast or features that can be tracked in the experimental interaction. Brominated, chlorinated, iodinated and deuterated plastics can be produced and, when integrated with micromachining, can be formed into complex structures. The group is also developing metallic foam production methods.

Development of targets for EPAC is a key goal for the group. Providing user support for the broad experimental program will require a number of key technologies. The group is leading the way in the development of targetry systems to achieve this.

Tape Targetry

The integration of a high specification tape drive with high stability in the laser focus direction (1 micron) enables shot rates of up to 10Hz to be achieved without re-focussing. In addition, the groups complex tape target manufacture capability allows structured and coated samples to be supplied.

Liquid Targetry

In collaboration with the user community the group has developed a liquid target system that can be used for high-rep rate experiments. We continue to develop the system and are researching the possibilities of using it as a plasma mirror system for EPAC. The system is easily configurable for liquid leaf, or liquid jet/droplet targets.

Robotic Assembly

The TAAS system is an integration of robotic arms and grippers with vision recognition software and automated glue dispensing and curing and it allows the group to manufacture arrays of targets for high rep-rate experiments. These samples can be coated and machined to size in batches before being spread on a carrier plate. The robot system can then recognise appropriate targets and assembly to the required tolerances – reducing production time and staff effort.

Target Fabrication has an extensive range of characterisation equipment available to it that has been specifically chosen for the complex metrology challenges that are provided by high power laser targets. Utilising optical, touch probe, electron and atomic force microscopy, a full characterisation service is available to ensure that the targets we produce are to the highest specification. Our trained target engineers can advise on appropriate characterisation techniques for different target designs and will discuss with you the most appropriate parameters for your target design.

The UPLiFT project enables the group to invest in the development of technologies to produce Inertial Fusion Energy (IFE) relevant targets. We are investigating the suitability of 2-Photon-Polymerisation to produce the micro structured foam and shell targets that hold the fuel. We are using micro and macro fluidic devices to produce plastic shell targets that require extremely high tolerances on diameter, form, wall thickness and surface roughness. This work will support UK academics carrying out experiments but also will enable us to upskill the UK community in fusion target manufacturing. We are working with a number of universities and national laboratories to meet our goals.

Experiments are often fast moving and change rapidly as the science evolves, targets are often costly and time consuming to produce. The advancing field of AM is enabling the group to be more cost efficient, adaptable and responsive in its support of the user community. We have capabilities in medium resolution printing that enable support structures and jigs to be manufactured within a day. We have high resolution (5-10um) printing that provides the ability to manufacture target components quickly and to high specifications and we have sub-micron resolution capabilities with our 2PP system.  To achieve the best results, we have skilled teams that are able to maximise the use of these systems and push AM to its limits in target manufacture.