f c e e r g s o r a c l r a t o m a n e t Gerard Willering S t a b i l i t y o f S u p e r c o n d u c t i n g r C b l e R u t h e f o r d a s PrefaceThe work described in this thesis results from an extensive collaboration between the special chair for Industrial Application of Superconductors in the Low Temperature Division at the University of Twente and the Magnets, Superconductors and Cryostats group at CERN. The research has been carried out at CERN as well as at the University of Twente and it is funded by both institutes. Part of the cable samples were prepared by GSI in the frame of research collaboration on cable stability.I am very grateful to the members of these groups for giving me the opportunity to perform the research, for their interest and useful discussions.i ContentsPreface i Chapter 1 IntroductionAfter the discovery of superconductivity in the beginning of the 20 th century the understanding of the phenomenon has grown. Practical conductors are produced for various magnet applications. Although the number of superconducting materials is high, only a few can be used in high-field and high-current density applications. This thesis deals with cable stability, with the focus on application in accelerator magnets.In this chapter a brief overview of the existing and near future accelerators and their superconducting magnets is presented. The most recent superconducting accelerator, the lhc and the near future superconducting accelerator sis 300 are described.The phenomenon of superconductivity is shortly discussed and practical superconductors are introduced with an emphasis on strands and cables. Different types of cables are presented and the relevance of this thesis for in particular the Rutherford type of cable is discussed.The terms quench and recovery are introduced. The importance of research on stability is illustrated by the large number of training quenches in the lhc main dipole magnets. Superconducting accelerator magnetsIn High Energy Physics the interaction of elementary particles is being studied. Many particle accelerators have been constructed to accelerate particles and collide them at high energy. Synchrotron accelerators provide a circular track with RFcavities to accelerate bunches of particles each cycle.Synchrotron accelerators require dipole magnets to bend the particle beam and keep it in its circular track. Quadrupole magnets are used to focus and defocus the beam and higher-order magnets correct field distortions and chromaticity. The collision energy depends on the magnetic field in the aperture of the dipole B a (T) and the bending radius of the dipole magnets r d (km) following E ≈ 0.3B a r d (TeV). The limitation in the track circumference is strongly dictated by the amount of material and the costs involved. In normal conducting magnets iron is applied to enhance the electromagnetic field produced with copper windings. The magnetic field in iron saturates at about 2 T, therefore the needed amount of copper windings and the costs involved increase strongly for hig...