Measurements investigating the embedding procedure of the Wendelstein 7-X non-planar coils

One manufacturing step of the Wendelstein 7-X non-planar coils is intended to generate a mechanical prestress between winding pack and casing. To document this “embedding” procedure, we performed several temperature and electric resistivity measurements and geometric surveys before, during and after the embedding. We also investigated the behaviour of quartz sand, used to fill the gap between winding pack and casing, under pressure. The results of the whole body of investigations are consistent with the assumption that the achieved prestress is significantly lower than initially intended.