AC Loss Modeling of a Full-Size ITER CS Module

Abstract

Thorough analyses of electromagnetic transients in superconducting coils for fusion magnets are necessary to compute the losses arising in time-varying operating conditions and correctly design the cryogenic system. The challenge of these analyses, when using numerical methods, is related to the high number of degrees of freedom required to discretize large-scale magnets wound with cable in conduit conductors (CICCs), which include hundreds of composite strands. This study is focused on the central solenoid (CS) of the ITER magnet system, composed of six modules, each wound with several CICC for a total length of 6 km. The numerical code THELMA and an analytical model based on a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">single time constant</i> —previously applied to analyze the tests of a 44-m-long single-layer solenoid, referred to as CS Insert (CSI)—are scaled up to calculate losses during factory acceptance tests (FAT) at the General Atomic (GA) in Poway (US). We demonstrate, by comparison with experimental data, the possibility of predicting the losses in the CS module by projecting the results obtained in the CS Insert subsize test, a single-layer solenoid tested at the National Institute for Quantum Science and Technology (Naka, Japan). The application of a numerical model discretizing the conductor with a few tens of subcables to a full-scale fusion magnet is very demanding. A novel methodology is proposed to abate the computational burden, based on reducing the number of turns involved in the calculation, still retaining a high level of accuracy in the loss assessment.