Design and analysis of the cryostat of the ITER magnet cold test bench

Abstract

ITER is constructing a Magnet Cold Test Bench (MCTB) to evaluate the discharge characteristics, quench protection, ground insulation, and leakage rates of all ITER toroidal field (TF) coils and the poloidal field 1 (PF1) coil, ensuring reliable operation when integrated into the ITER tokamak. The MCTB cryostat, the primary component of the bench, is designed for compatibility with TF and PF1 configurations, providing a thermally insulated and high-vacuum environment for the coils. This paper begins with an overview of the cryostat structure, encompassing its shells, multi-layer insulation (MLI), magnet supports, and pressure relief device (PRD). Next, thermal analyses are performed to quantify the thermal conduction from the magnet supports to the tested coil and radiation from the MLI. Results demonstrate that even when the liquid helium pipeline temperature of the cold plates rises to 30 K, the thermal conduction load on the coil via the supports remains well below the 400 W limit. Regarding radiation heat, when the number of MLI layers increases to 50, the total radiation heat on the coil for the TF and PF1 configurations is approximately 839 W and 799 W, respectively, both below the 1000 W threshold. Additionally, assessments of the cryostat shells’ structural responses under varying loading conditions reveal that a 10% safety margin in structural strength is maintained, and the buckling load multipliers exceed the corresponding critical thresholds even under the worst operational load, demonstrating the absence of plastic collapse and buckling instability. A simple sealing scheme is proposed to address the pre-tightening problem of large-diameter sealing between cryostat shells, incorporating an effective suppression solution for flange slippage during sealing. Finally, significant developments in the cryostat’s manufacturing and future production plans are reviewed. This paper can provide valuable technical guidance for the design of other magnet test platforms.