NSTX-U Vacuum Vessel design modification

The NSTX-U requirements will double the Toroidal Field (TF), Plasma Current (Ip), Beam Injection Power, and extend pulse length. The larger centerstack requires re-aiming of the Multi Pulse Thomson Scattering (MPTS) lasers and Vacuum Vessel (VV) modifications at Bay L. The second neutral beam requirements include larger tangency radii and thus a VV modification at Bay K and Bay J. A cap design for a new weldment was developed to achieve these larger beam trajectories without losing the utility of the Bay J port for diagnostics. Analyses of loads indicated the need for reinforcements of the vessel at the midplane. NSTX has 6 picture frame type Resistive Wall Mode (RWM) coils around the exterior circumference of the vacuum vessel; each coil surrounds pairs of ports. The modifications needed for the upgrade were intended to minimize the impact to the RWM fields at the plasma. A Pro E global model segment was used to model the vacuum vessel. ANSYS was used to apply loads and investigate reinforcement configurations. A focused effort and analysis produced a design capable of achieving the desired performance of the upgrade while maintaining utility and continuity of RWM coil physics pre- and post-upgrade physics performance. The installation of the Bay J-K and Bay L Port Caps was completed and the reinforcing weldments have been partially installed.