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Code Development and Validation Towards Modeling and Diagnosing Current Redistribution in an ITER-Type Superconducting Cable Subject to Current Imbalance

L. Zani, P-E. Gille, C. Gonzales, S. Kuppel, A. Torre

Fusion Science and Technology / Volume 56 / Number 2 / August 2009 / Pages 690-694

ITER / Eighteenth Topical Meeting on the Technology of Fusion Energy (Part 2) /

In the framework of ITER magnet R&D activities, a significant number of conductor short-samples or inserts were tested throughout the past decades, either for development on cable layouts or for industrial qualifications. On a certain number of them critical properties degradations were encountered, some of which were identified to be caused by current imbalance between the different strands bundles twisted inside the cable.

In order to address the analyses of those samples as reliably as possible, CEA developed a dedicated home code named Coupled Algorithm Resistive Modelling Electrical Network (CARMEN) having basically two specific functionalities:

-a first routine which is devoted to compute strand bundles trajectories, with bundles down to the individual strand scale. This point allows to obtain a realistic E(J) law over the full conductor length

-a second routine which is devoted to model inter-bundle currents redistribution, taking into account the magnetic field map. It basically makes use of a relevant discrete electrical network with defined sections including E(J) law obtained from the above-mentioned subroutine

As a result, the E-J or E-T curves can be calculated and compared to the experimental data, provided adapted inputs on sample features are considered, such as strand contact resistances in joints, inter-bundles resistances or cable geometry.

In a first part, the paper describes the different hypotheses that built the code structure, and in a second part, the application to the ITER TFCI insert coil is presented, focusing particularly on the validation of the potential use of the code to stand as a diagnostic tool for currents imbalance probing.

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