Quench Safety and Quench Protection of Metal-Insulated Superconducting Coils for the Next Generation Sample Environment Magnets

Topic  6
Main supervisor S.Mühlbauer (Sebastian.Muehlbauer@frm2.tum.de)
MLZ institution TUM
Local supervisor 1 M.Gehring
Institution Bilfinger-Noell
Local supervisor 2
Local supervisor 3
Local supervisor 4
Title Quench Safety and Quench Protection of Metal-Insulated Superconducting Coils for the Next Generation Sample Environment Magnets
Description Due to their unprecedented current density in high magnetic fields, high temperature superconductors (HTS) represent the future technology for sample environment magnets at MLZ. With HTS, higher magnetic fields can be achieved with magnets that are considerably lighter and smaller compared to past generations, greatly reducing stray fields with a more efficient active compensation. While coils made from low temperature superconductors (LTS) are in routine use, the step towards HTS imposes major technological challenges building reliable and safe magnets. This particularly concerns the quench safety, caused by the entirely different quench characteristics of HTS materials: Typically operated with a small temperature margin, LTS coils exhibit a fast quench propagation that – in the case of a local quench – quickly leads to a quench of the whole coil that equally distributes the heat-load and reduces the risk of a local destruction. In conclusion, while LTS coils are prone for quenching, they typically withstand quenches without any permanent damage. In contrast, due to their high transition temperatures, HTS coils exhibit a larger temperature margin, hence are more resistant to quenching. However, they are characterized by a slow quench propagation that quickly leads to a large heat-load and a local destruction of the coil in the rare event of quench. A novel Ansatz approach is the use of non- or metal insulated coils, where the HTS conductor is co-wound with metal ribbons. In the case of a quench, the current redistributes inside the coil, leading to inherent quench safety. A drawback of metal insulated coils is their slow stabilization times, issues with field stability and asymmetric skew forces in the event of a quench. Up to now, metal-insulated coils are a field of academic research and not commercially available. In a joint project with Bilfinger-Noell, we propose to build a demonstrator system using the novel metal-insulated technology to systematically examine its quench behavior and the involved magnetic field forces. Moreover, it is planned to examine the field stability and quality. Our project provides an important key technology for the next generation of magnets for sample environment at MLZ.