Design of self-centering support system for 1.5 T MRI cryostat

Present-day whole-body MRI scanners are of “zero boil-off" type which hardly need liquid helium refill. To realize this requirement, the cryostat housing of the superconducting magnet system and many several sub-systems need highly innovative design. This includes the state-of-art design of the support system for the large cold mass (~ 4 tons) meeting the stringent requirements of minimum heat input to the LHe-bath, possessing high strength to take care of the high thermo-mechanical stresses, heavy load, transportation and keeping the magnet center unaffected through self-regulation. In this paper, we report coupled thermomechanical and modal analysis of the support system, performed using ANSYS to study temperature deformation and stress in the support assembly. The design includes mechanical strength, minimum resonant frequency, heat load calculations, maximum pretension force and allowable accelerations for the maximum pre-tension. The design incorporates carbon- glass (HS carbon) rods supporting nearly four tons cold mass during assembly, shipment and the normal operation of the MRI magnet.