Constantinos Minas

Vibration isolation of superconducting magnets

In order to improve image resolution and magnetic field uniformity in a magnetic resonance imaging device, the vibrations and loads produced by the cryocooler are isolated from the superconducting magnet and cryostat. The vibrations and loads are isolated through the use of flexible, laminated copper connectors and rubber mounts.

Three-dimensional thermal stresses in a superconducting coil assembly

The three-dimensional thermal stresses in a solenoidal superconducting coil assembly are examined and evaluated. The superconductor composite is modeled as an orthotropic material with three planes of elastic symmetry, with mechanical properties derived from experimental measurements at 293 K and liquid-nitrogen temperature, adjusted according to the applied temperature range. The cooldown stresses in the coil in a stand-alone configuration are compared to the stresses due to the temperature field simulated for a quench. The quench thermal transient analysis creates a nonuniform temperature profile in the range of 30-250 K. A two-dimensional and a three-dimensional temperature field are used in the three-dimensional stress analysis. When comparing the stresses in the cooldown and temperature fields, the results indicate an increase of the tensile hoop stress by a factor of four and an increase of the compressive hoop stress in the coil by a factor of eight. Similar analysis is performed on the superconducting coil assembly, which includes a part of the glass-epoxy composite coil form and the aluminum support structure, and the results are examined and evaluated. The analysis is performed in the cylindrical coordinate system by using the commercial package ANSYS.