The general target engineering process for new target designs is as follows:
Target Fabrication reviews physics requirements, design, and schedule
The Shot RI (who is either the Principal Investigator [PI] or the liaison scientist) brings the target design and physics requirements to Target Fabrication as soon as an experiment is approved, and before it is scheduled, to discuss design feasibility. For Inertial Confinement Fusion (ICF), High Energy Density (HED), and National Security Applications (NSA) experiments, approval from the appropriate council is typically 9 to 12 months (at a minimum) before an experiment is scheduled for a shot. For Discovery Science (DS) experiments, approval by the NIF director is typically given 18 to 24 months before the shot. A drawing of the target should be provided with sufficient information for NIF Target Fabrication to assess the cost and effort required for development, production, and fielding. The drawing should include dimensions and all materials to be used and should call out the use of any hazardous materials. Target Fabrication will provide design feedback, discuss target materials research and development (R&D) needs, and create a time estimate.
Target Fabrication performs engineering analysis and prepares drawings
Once the experiment is scheduled, which happens between 6 to 12 months before the shot date, Target Fabrication assigns a target engineer to work with the Shot RI and prepare a conceptual design and drawings indicating dimensions and tolerances. Focus is put primarily on experiments occurring six months out on a rolling basis. Of course, earlier identification of any target design issues always increases the margin of success.
Experts review and sign off on target design
Target specifications must be agreed to well before the target is built. A target request (TR) initiates the fabrication process (see Figure 7-1). Before fabrication formally begins, these items must be reviewed: laser safety (unconverted light and backscatter), debris (calculation of ejected material), alignment (agreement on needed fiducials, measurement techniques used and verified), self-consistency checks, special materials, and target mass. The Shot RI works with representatives from target engineering, the alignment team, the metrology group, and target operations to uncover and resolve any physics, safety, and cleanliness issues early in the process. Any dependencies of the design on target materials R&D should also be identified. The Shot RI, together with NIF, must also develop a target alignment plan/strategy. Typically, this process runs continuously from the approval of the experimental proposal, and all issues of the types described above are resolved and any problems mitigated three months before a scheduled shot date.
Target is fabricated and metrologized, electronic RVP is generated, and nonconformance issues are resolved
If it is determined during target metrology that a target or target component does not meet specifications, the target will be evaluated by NIF’s Management Review Board (MRB) to determine if the target should still be shot, if the specification(s) was/were reasonable, and if the experiment can be performed as planned.
Target is accepted and shot
Target delivery to the NIF facility is expected to be no later than two weeks before the scheduled shot date. Shot RI review of the metrology data in the RVP needs to be done at least three weeks before the shot date in order to confirm that all aspects of the target are consistent with what is required to perform the shot.
