Large-Aperture 6 T Dipole for Ion Storage Ring

ATC requests Phase 1 SBIR funding to develop a 2-layer NbTi Cable-in-Conduit (CIC) conductor suitable for a large-aperture 6 T dipole. ATC has successfully developed a single-layer 13 kA NbTi CIC cable, and our collaborators at Texas A&M University (TAMU) have successfully used it to make a 3 T dipole suitable for the arcs of a 100 GeV Ion Ring that has until now been the baseline design for JLEIC. The recent NAS report cautions that 200 GeV ion energy would likely be needed, however, to cover the range of energy required for the objectives of the EIC project. ATC has developed a design for a cost-effective large-aperture 6 T dipole based upon a two-layer 23 kA NbTi CIC cable that preserves the simplicity of fabrication that has been demonstrated in the 3 T model. The proposed 23 kA cable is a challenging development. The issues of the compliant interlayer and sheath compression to support stable bending the coil ends, cryogen transport, and quench protection have been studied in short cable segments. All issues appear to be compatible with the requirements for the 23 kA cable and for forming the dipole winding, but much work must be done to optimize the cable parameters and prepare and test short model windings. In the proposed Phase 1 effort ATC will develop a 2-layer cable-in-conduit conductor and the coil technology to use it to make the windings for a 6 T arc dipole. The objectives of the Phase 1 effort are to optimize the 2-layer CIC by building and evaluating medium-length samples, to develop a model of out motorized bend tooling that will form the flared U-bends for the dipole, to short-sample test 2-layer cables containing a single superconducting strand in registration with 35 bronze strands, and to fabricate a first 3-turn winding in the geometry for the 6-T dipole winding. Pending success in those objectives, a follow-on Phase 2 effort would make modifications arising from what we learn and then build and test a first 6 T 1.2 m model dipole. The proposed CIC dipole development offers a cost-effective path to establish a credible basis for a 200 GeV re-embodiment of the JLEIC design. It uses half the superconductor and 1/3 the number of turns that was required in a recent prototype cos  dipole developed by IHEP and GSI that has the same field strength and aperture. As such it directly addresses the primary challenge to the JLEIC design that was expressed in the NAS report. The 2-layer cable has several potential commercial applications, for which ATC has developed a preliminary Business Plan: (1) 40 kA CIC using Nb3Sn for compact tokomaks for fusion energy (collaboration with PPPL); (2) 15 kA CIC using MbB2 for a superconducting generator for >5 MW wind turbines; and (3) 25 kA CIC fusing Nb3Sn and Bi-2212 or 16 T dipoles for future hadron colliders.