Dynamic response analysis of superconducting coils in Wendelstein 7-X and mechanical quench test

The Wendelstein 7-X (W7-X) modular stellarator is under construction at the Max-Planck-Institut fur Plasmaphysik in Greifswald, Germany. The W7-X magnet system contains 70 superconducting (sc) coils which are supported by a massive central steel ring structure via bolted connections and by numerous welded as well as gliding inter-coil elements. Load tests on prototypes of bolted coil to support ring connections whose flanges partially open during high field operation, and of sliding support structures between the coils showed that stick-slip events at their contact surfaces cause shock waves. In order to assess the risk of a shock-induced quench of the superconductor, one of the coils was subjected to impact loads - the so-called mechanical quench (MQ) test - in the course of the cryogenic acceptance tests at CEA in Saclay, France. No quench could be triggered even with the lowest coil stability margin. The paper demonstrates that the amplitudes of the shock waves in the W7-X magnet system are comparable to those generated by the impacts in the MQ tests. For that purpose, finite element (FE) models of both W7-X and the MQ test simulating the dynamic responses were developed and successfully validated against measurements. (C) 2011 Elsevier B.V. All rights reserved.