Cooldown Analysis of a Conduction-Cooled Superconducting Magnet for Magnetic Resonance Therapy(MRT)
A three dimensional finite element model of the cooldown process and the resulting thermal stresses for a cryogen-free superconducting magnet used in interventional magnetic resonance therapy is examined and evaluated. The magnet cartridge consists of two cylindrical halves connected together by four structural posts. The magnet cartridge is cooled primarily by conduction cooling. The cooldown heat load from the cartridge can be removed in two ways; with cryogens via a heat exchanger attached to the cartridge, or via a cryocooler coldheads operating as the heat sink. The model is used to predict the fastest allowable cooldown time without introducing unacceptable stresses in the magnet. The predicted cooldown temperatures are compared to the measured performance. The cooldown stresses are presented and discussed. The model was built in Patran 3 as the preprocessor and the solution was run in ANSYS.
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