Design, construction and test of a 113-mm bore solenoid with NbTi cable-in-conduit superconducting windings

We have designed and constructed a 113- mm-bore solenoid using a cable-in-conduit type conductor with NbTi composite and copper strands as a focus for practical conductor fabrication techniques and coil winding methods using such conductors. In addition, the finished coil provides the opportunity for global tests of the performance of this type of conductor in a real coil that produces high field (∼8 T) and uses a long (340-m) section of conductor. The conductor cable is a concentric layer type containing 19 triplex strands made from 0.7-mm-diam wire. The superconducting strands are contained entirely within the outer layer of the cable and thus are fully transposed. The cable is jacketed with stainless steel tubing; the overall conductor diameter is 8.6 mm. Induction heaters, voltage taps, pressure taps, and temperature sensors are installed in the windings to aid in stability measurements. Flow to the coil is provided by either a blowdown system or a piston pump capable of providing 20 g . s^-1. Details of both conductor and coil fabrication are presented, and we report initial stability measurements. Results are compared to similar tests on short test conductors in an external field. Plans for future testing are also discussed.