Target Area design basis and system performance for the National Ignition Facility

A description of Target Area systems performance shows that the target area conceptual design can meet its performance criteria. Before the shot, the target area provides a vacuum of < 5 x 10-5 Torr within 2 hours. A target, cryogenic or non-cryogenic, is placed to within 1 cm of chamber center with a positioner that minimizes vibration of the target. The target is then aligned to ≤ 7 μm by using the Target Alignment Sensor (TAS) system. The viewers in this system will also determine if the target is ready for illumination. Diagnostics are aligned to the necessary specifications by the alignment viewers. The target is shot and data is collected. Nearly all tritium (if present) is passed through the vacuum system and into the collection system. The analysis that supports the target area design basis is a combination of careful assumptions, data, and calculations. Some uncertainty exists concerning certain aspects of the source terms for x-rays and debris, material responses to this energy flux, and the full consequences of the material responses that do occur. For this reason, we have selected what we believe are conservative values in these areas. Advanced conceptual design activities will improve our understanding of these phenomena and allow a more quantitative assessment of the degree of conservatism inherent to the system. However, the results of this preliminary survey of target area operations indicate an annual shot rate of > 600 (for the mix of shots shown in Table 1) is feasible for this set of target area systems