Stress analysis and mechanical tests for Demo Poloidal Coil

Japan Atomic Energy Research Institute is developing the Demonstration Poloidal Coils which consist of two Nb-Ti pulse coils and a Nb₃Sn pulse coil using a forced-flow conductor. Three-dimensional and two-dimensional finite-element models were used for the stress analysis of the coil system and each pancake, respectively. The coil system, consisting of three coils, was analyzed to estimate the deformation and the stress on coils and support structures for the mirror and cusp operation modes. The maximum stress appeared at the innermost turn. This was found to be due to the inner pressure increase generated by the coil quench. The calculated stresses were within the allowable stress limits for the Japanese Cryogenic Steel used.