Superconducting magnets

Abstract

The properties of practical `high-field' superconductors are outlined and related to the theory of type II superconductors. Their unexpected and disappointing behaviour when first wound into coils for the production of high fields is described. This problem is shown to arise from the nature of the current distribution in such materials and the consequent dissipation under conditions of changing current. The factors affecting this dissipation and the thermal stability of the materials are discussed together with means for achieving stable operation - in particular the use of composite conductors. Some of the engineering problems associated with the further development of large superconducting magnets are set out; for example, protection against burn-out, the support of the large forces developed and the introduction of current to the magnet. The article concludes with a brief description of some currently planned superconducting magnets, their applications and their economics.