Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers

An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the comprehensive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effects in actual magnets of the thermal stress changes from cool-down and the Lorentz forces during magnet excitation