Numerical study of the elastic-plastic cyclic deformation of the 'GLOBUS-M' compact tokamak central solenoid

The "GLOBUS-M" is a compact resistive tokamak with a central solenoid (CS) wound around the inner portion of the toroidal field coils. The magnetic field at the solenoid axis amounts to 8.3 T. The CS incorporates two layers of conductor (CuCr copper alloy) baked into insulation. The solenoid is designed to sustain 80.000 energizing. During each loading cycle the solenoid is subjected to the radial forces accompanied with the vertical compression. The most loaded region has been considered and modeled with the use of 2D axisymmetric finite element (FE) model. The model includes two conductor turns baked into insulation compound, copper cooling tubes and solder. The stress analysis shows that there is some plastic deformation in the copper tube and solder during loading and there is some back plastic deformation in the solder during unloading. The reloading does not cause any change in the solenoid stress-strain state in comparison with the case of loading. The number of cycles to failure has been simulated for all metallic components of the solenoid.