Critical Current Behavior of PIT Nb3Sn Strands Under Transverse Load Using Finite Element Analysis.

摘要

Superconducting Nb3Sn wires are used in high field magnets for applications such as ITER, an experimental fusion reactor in France, and the next upgrade to the Large Hadron Collider. Unfortunately Nb3Sn is very sensitive to strain. During manufacturing and operation the wires are subjected to transverse compression and will experience strain, which can severely degrade current-carrying performance. In order to predict the performance capabilities of this material when used in these applications, it is important to know how a wire will react to given conditions that it will experience during manufacturing and operation.;While Nb3Sn properties are generally studied experimentally it is difficult to perform tests on even single wires, let alone cables, given the cost of the experiment and the high background fields necessary to electro-mechanically characterize the material. Each wire is also composed of thousands of micrometer-size filaments each of which determines the superconducting behavior. Individual filament performance cannot be measured experimentally therefore Finite Element Analysis (FEA) is employed to estimate the strain felt by each filament and predict Nb3Sn wires' behavior.;In this work, seven different Nb3Sn wire architectures were examined with finite element analysis under different transverse loading conditions simulating manufacturing and operational conditions. The FEA models will be discussed in detail together with all the parametric studiesperformed. After extracting the principal strains of each element, it is possible to use an available scaling law to determine the current-carrying capacity of the wire. This allows for qualitative predictions of the critical current behavior of each wire under varying strain conditions and comparison to available experiments.