Structural analyses, sensitivity analyses, and independent confirmatory analyses of the IGNITOR magnet system

Ignitor has been the first experiment proposed and designed to reach ignition conditions in magnetically confined plasmas. It is a compact, high field machine based on the physics developed primarily by the Alcator series of experiments. Each refinement of IGNITOR has drawn from a common set of `tools': Bitter plate copper magnets; bucking/wedging interactions of the CS and TF coils; and passive and active preload mechanisms to offset vertical tension in the inner leg and tension in the horizontal leg. Elements of the IGNITOR design are statically indetterminant. Examples of multiply redundant load paths used in other reactor designs are cited. Despite a large body of historical work confirming the structural feasibility of IGNITOR, it still is erroneously perceived as more challenging than other tokamak designs. Past US analyses are recalled: US contributions from independently derived models are described and are compared with the latest IGNITOR project analyses. Differences in modeling philosophy are presented, and results are compared. Recent US analyses employ non-linear path dependent friction of a 2 coil segment. Sensitivity studies of fit-up tolerances and, uncertainties in material properties are presented. While there are some small differences in results, these analyses independently confirm the benefits of the major structural elements used in IGNITOR.