Time-Dependent Thermo-Electro-Magneto-Mechanical Analysis of the TF Coil in Damavand Upgrade Tokamak With Longer Pulse Operation

Abstract

To reach a more efficient plasma operation, a new configuration is planned for Damavand tokamak toward a longer pulse scenario. The current pulses in the magnetic system will be ten-times extended. This introduces major thermal impacts on the toroidal field (TF) coils due to Joule heating in addition to electromagnetic loads. Each TF coil consists of a winding pack (WP) with epoxy-impregnated glass-mica tape enclosed in an aluminum case. In this work, the combined thermo-electro-magneto-mechanical behavior of the TF coil components is investigated in the long pulse operation. A computational fluid dynamics (CFD) model has been involved to simulate a water cooling in the TF coil using COMSOL. Therefore, the study involves various analyses on the Lorentz force density, thermal load due to the Joule heat, stabilized temperature, heat dissipation, stresses and strains, and TF deviation in vacuum vessel due to the TF coil deformation. Every shot introduces a rise in the temperature of the coil. Thus, depending on the cooling conditions, in a series of consecutive shots, the temperature reaches a limit which is crucial for the mechanical analysis. As a result, although the thermal stress on the WP is highly increased in every long pulse, the total stress (i.e., combined thermal-magnetic stress) decreases compared to the value in the presently short pulse operation. The total stress in the WP can be lower than its magnetic stress due to an increase in elasticity of the coil during the longer pulses, while this result is the opposite for the casing and the epoxy resin.