Superconducting magnets

Abstract

T h e properties of practical high-field' superconductors are outlined and related to the theory of type I1 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 operationin 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.

Earthquake ruptures with thermal weakening and the operation of major faults at low overall stress levels

“…These works suggest that intergranular slip occurs at a small number of the contacts, and the local slip rate is about the same as the macroscopic slip rate of the fault. On the other hand, there are observations of thin but finitely thick shear zones in both exhumed faults [ Chester and Chester , 1998; Chester and Goldsby , 2003; Chester et al , 2004; Heermance et al , 2003; Mizoguchi and Shimamoto , 2004] and specimens after frictional experiments at high slip rates [ Beeler et al , 1996; Mizoguchi and Shimamoto , 2004]. These shear zones are recognized by shape‐preferred orientations of platy minerals, which clearly indicate that the total shear strain is distributed within it.…”

The physical properties of composite materials

“…The corresponding dynamic stability criterion is given, for a composite consisting of alternate layers of superconductor and normal metal (e.g. Cu), by the relation [148][149][150] …”

Flux-pinning in multifilament niobium by dislocation cell boundaries

“…One of the ways of achieving stabilization against flux jumps is to make the conductor diameter as small as possible [1]. Commercial superconductors are, therefore, fabricated in the form of fine multi filament wires embedded in a matrix of copper or aluminium.…”