Stress analysis of solenoids that develop gaps

Several large superconducting magnets recently built or under construction at the Oak Ridge National Laboratory use ventilated winding-pack designs. Due to external constraints, it is not always possible to develop enough prestress to ensure compressive layer-to-layer interface pressures. Unless there is some mechanism to support tensile interface pressures (such as epoxy bonding, which is not possible in ventilated magnet designs), the magnet will develop gaps at these interfaces. Presented herein is a theory for determination of the nonlinear mechanical behavior of axisymmetric solenoids that can develop frictionless gaps which may open and close during magnet cooldown and energization. Also discussed are the implementation of this theory within a computer program and an example application of this theory to several magnets.