The invention generally relates to superconducting magnets, and more particularly to superconducting magnets with an improved support structures for supporting superconducting coils.
Superconducting magnets are used in many applications, such as magnetic resonance imaging systems and cyclotron magnet systems. Superconducting magnets generally have a plurality of superconducting coils for generating a magnetic field and one or more support members for supporting superconducting coils. The “superconducting coil” is referred to as “coil” hereinafter for simplicity.
When the superconducting magnets are energized, the coils produce axial electro-magnetic (EM) forces and radial EM forces. The one or more support members are used for supporting the coils against the axial EM forces. The radial EM forces are generally accounted for by the coils' own hoop stresses, which result in hoop strains and radial expansions in the coils. Such radial expansions of the coil can cause frictional movements at the contact interfaces between the coils and the one or more support members. The frictional movements generate heat, which can quench the coils and lead to magnet instability of the superconducting magnets. This is particularly noticeable at low temperatures, such as liquid helium temperature, since the coils have very small thermal capacity and a small thermal disturbance can raise the temperatures of the coil to exceed its threshold, causing the coil to quench.
Some conventional superconducting magnets allow some frictional movements at the contact interfaces by having more superconducting or normal metal materials in the coils to absorb the thermal disturbances. However, superconducting materials are expensive and adding more material in the coils results in the increased production cost. In another conventional superconducting magnet, the coils are directly bonded to the support structure. The bonding strength at bonding interfaces makes the one or more support members move together with the coils. However, inconsistent movements can cause cracks at the bonding interfaces, which results in thermal disturbances to the coils.
Therefore, there is a need to provide superconducting magnets with an improved support structure to achieve better magnet stability.