Nb3Sn SuperCIC Outsert and REBCO Conformal Insert for an 18 T Collider Dipole

Accelerator Technology Corp. (ATC) and the Accelerator Research Lab (ARL) at Texas A&M Univcrsity have collaboratively developed a novel conformal winding methodology that could make it possible to orient all of the REBCO in a winding in this favorable orientation, so that the quantity of expensive superconductor would be minimized. ARL has submitted a proposal to the university program of DOE-HEP to develop the Conformal Winding technology and use it to fabricate the insert windings for an 18 T hybrid dipole suitable for future hadron colliders. ATC has developed an innovative technology for a Nb3Sn outsert winding that could be assembled with ARL’s REBCO insert to make the hybrid dipole robust and cost-effective. ATC requests SBIR funding to develop its SuperCIC cable using high-performance Nb3Sn wire, and to develop flared-end windings in the geometry required for the hybrid dipole outsert. The two efforts are close companions – ARL will develop the REBCO conformal winding insert, and ATC will develop the Nb3Sn SuperCIC outsert. The two developments would proceed largely in parallel until first models of both windings have been built. The SuperCIC cable is fabricated by cabling Nb3Sn wires onto a perforated center tube, then the cable is pulled as a loose fit through a high-strength sheath tube, and the sheath is drawn onto the cable to compress the wires against the center tube and immobilize them. A robotic bend tooling has been developed that can form small-radius bends and yet preserve the interior registration of the wires without wire strain. The Nb3Sn CIC can thereby be formed into the flared-end windings needed for the outsert of the 18 T dipole. The CIC structure provides stress management at the cable level, and cryogen can be flowed through the center tube so that the outsert could be operated at 5 K (necessary for Nb3Sn) while the insert could be operated at ~20 K (without penalty using REBCO). The option to operate the insert hotter could be a major benefit in an ultimate-energy hadron collider, where synchrotron radiation will deposit large heat load near the beam tube. During the Phase 1 project ATC will develop and evaluate short flared-end windings of Nb3Sn SuperCIC and test them as inserts in BNL’s 11 T background field dipole. Following those tests, ATC will fabricate a 180 m segment of Nb3Sn SuperCIC, form it into a 4-layer flared-end outsert winding, and install it in a steel flux return. This model dipole can serve a succession of roles in follow-on projects: It can be operated at 4.2 K as a 7.5 T background field dipole (TAMU4) with 7x10 cm2 clear aperture, in either BNL’s or LBNL’s test cryostat. This would provide a first test bed for the performance of Nb3Sn SuperCIC outsert winding technology. It would be the first task of a follow-on ATC Phase 2 effort if the Phase 1 is successful. The conformal REBCO dipole insert winding could be installed in its aperture and connected in series to make an 11.3 T dipole (TAMU5), which would provide a first test bed for the conformal winding technology. This would conjoin ATC’s outsert development with ARL’s insert development, and constitute the second task in the Phase 2 effort. A second 4-layer Nb3Sn SuperCIC flared-end sub-winding can be added and connected in series with the TAMU5 winding to make the first-ever 18 T flared-end dipole. The innovations of ATC’s Nb3Sn SuperCIC outsert and ARL’s conformal REBCO insert thus have the potential to provide a robust basis to achieve many of the objectives of the Magnet Development Program. ATC has two specific product initiatives utilize the same innovations as does the solenoidal lens: a multi- zone NMR spectrometer, in which up to 10 ppb spectroscopy zones are produced in the bore of a single high-field spectrometer, and a pseudo-direct-drive generator for wind turbines, which could efficiently couple the low-rpm rotation of a blade hub to the high-rpm required for efficient electric power conversion.