Stress multipliers for the NSTX upgrade digital coil protection system

Conceptual design of the upgrade to NSTX, explored designs sized to accept the worst loads that power supplies could produce. This produced excessive structures that would have been difficult to install and were much more costly than needed to meet the scenarios required for the upgrade mission. Instead, the project decided to rely on a digital coil protection system (DCPS). Initial sizing was then based on the 96 scenarios in the project design point with some headroom to accommodate operational flexibility and uncertainty. This has allowed coil support concepts that minimize alterations to the existing hardware. The digital coil protection system theory, hardware and software are described in another paper at this conference. The intention of this paper is to describe the generation of stress multipliers, and algorithms that are used to characterize the stresses at key areas in the tokamak, as a function of either loads calculated by the influence coefficients computed in the DCPS software, or directly from the coil currents.