Materials technology for magnet insulation and bonding

Magnet coils come in many different sizes and shapes and operate under a variety of conditions. Electrical insulation may be applied directly to the conductor in the form of enamel or braid or it may be added during coil construction in the form of films and tapes. With such a range of coil types and size, there can be no single list of procedures and materials that covers all coils. However, this paper outlines the properties of a range of electrical insulation that is available for use in magnet coils and considers the conditions required for vacuum impregnation and for insulation with pre-impregnated materials. The same materials that are used to provide electrical insulation are frequently required to bond the main elements of the magnet to form one consolidated structure. Methods of assessing bond strength are considered and the interpretation of results on bonding and bond strength is reviewed, as is the effect of bond line thickness on joint performance. Dimensional changes that occur on heating and cooling are related to the practical situation that exists in magnet coils.