Design and Fabrication of a DC Feeder System of New TF Magnet Power Supply for Accelerator-Based In-Situ Materials Surveillance in Alcator C-Mod

Abstract

Advanced Plasma Material Interaction (PMI) science requires in-situ time and space-resolved measurements over a large area of Plasma Facing Component (PFC) surfaces to study fuel retention & recovery, erosion & redeposition, material mixing, etc. A novel PFC diagnostic technique Accelerator-based In-situ Materials Surveillance (AIMS) has been developed for Alcator C-Mod. At present, the AIMS covers a relatively small (35 cm) poloidal section of the inner wall PFCs at a single toroidal angle; an upgrade has been proposed which will enable nearly full poloidal (124 cm) and 40 degree toroidal PFC coverage. This paper introduces the design, analysis and fabrication of the new TF magnet power supply system for this upgrade. First, the design of the busbar system and its support structure is described, which are required to carry 15 kA current for long pulse operation of up to 25 minutes and fault condition of 400 kA for 1 second. Additional elements in the power supply system include a bidirectional crowbar, varistor protection assemblies, and a high current bus switch. Secondly, multi-physics analyses involved in the design are presented. Electro-magnetic analysis is performed to evaluate the spreading load of the two current-carrying busbars while Joule heating with thermal racheting analysis is to estimate the temperature rise in the components. Structural analysis taking into account dead weight, thermal expansion, spreading load and seismic load is performed. All analyses are completed using finite element analysis software COMSOL. Analytical calculations are included to validate the FEA results. The power supply system is ready for fabrication.