Structural design and analysis of a cryogen-free open superconducting magnet for interventional MRI applications

The structural design and analysis of a cryogen-free open superconducting magnet for interventional MRI applications is presented. The magnet assembly consisted of two identical halves connected together by four posts. The magnet separation allows a surgeon access to the patient within the field-of-view of the imaging system. Each half of the assembly consisted of three superconducting coils, a stainless steel bobbin, a copper thermal ring, and three overwrap rings. The suspension components of the magnet consisted of eight radial straps and eight axial rods. A structural analysis was carried out that considered the differential thermal contraction caused by the cooldown to the magnet cryogenic operating temperature, and the electromagnetic forces on the coils when the magnet is energized at the design current value. The results are compared to the equivalent stresses caused by a simulation of a quench that was initiated at the inner diameter of one of the superconducting coils. The post-quench thermal transient analysis predicted a nonuniform 3-D temperature field in the range of 10 to 178 K and asymmetric electromagnetic forces on the superconducting coils. The three dimensional structural model of the assembly was developed in ANSYS.<>