Study of impregnating materials for stable superconducting magnets

The cryogenic properties of impregnating resins were measured, and the instability of superconducting magnets was studied with reference to these properties. As impregnating materials, alumina powder filled, nonfilled, and irradiated nonfilled epoxy resins were studied. Cryogenic properties such as mechanical strength, thermal contraction, and thermal conductivity were measured. The minimum quench energies of impregnated short samples were measured. The training behavior of small sized impregnated coils was also studied by using the acoustic emission technique to estimate epoxy cracking in the coils. It was found that the mechanical, not the thermal, properties of the impregnating materials were the important factors for the stability of superconducting magnets.<>