Use of tapered key collars in dipole models for the SSC

Three 1-m Superconducting Super Collider type dipole magnet models were constructed and tested using tapered keys to lock interleaving Al alloy collars around the coils. This design enables the coil prestress to be created by hoop tension in the collars as the keys are pressed in, and minimizes the high coil overstress required to insert traditional nontapered keys. A description of the design includes a finite-element analysis along with an assessment of the forces needed to key the collars. It was found that collaring may be accomplished without exceeding 10000 psi coil pressure while producing in excess of 7500 psi coil pressure after collaring. Significantly, this design enabled Al collars to be used with their advantage of maintaining coil prestress during cooldown. Coil prestress measured during and after the collaring of the three models is described.