SBIR-STTR Award

Most superconducting accelerator magnets are presently based on a conventional “cosine theta” design. Typically, the magnet length vastly exceeds the aperture, and the loss in effective length from the ends (about a coil diameter in typical dipoles) is relatively small. However, for relatively short magnets such as those envisioned for the Interaction Region (IR) of the Electron Ion Collider (EIC) the end effects of the conventional design will result in a large relative reduction of the integrated field. To reduce the cost of EIC IR magnets, use of “direct wind technology” is being considered. Though the “direct wind technology” has been used in several low field magnets, it is yet to be demonstrated for a combination of high fields and large aperture magnets, such as those required in the EIC. A loss in magnetic length from the conventional ends increases the requirement of the field in the body of the magnet and hence the cost and technical risk of the magnet program. We propose to develop and demonstrate a medium field “direct wind” dipole with an “optimum integral design” approach that promises to have essentially no loss in effective length due to the ends. In the “optimum integral design” approach, the ends become an integral part of the magnet body - creating an effective azimuthal integral cosine theta distribution of the current density. This proposal will examine the “optimum integral design” for the ~3.3 T B0APF EIC IR dipole, which has a coil i.d. of 120 mm and a coil length of about 600 mm. In this case the estimated savings in effective length, about one diameter, is about 20%. During Phase I, a preliminary engineering design of the medium field EIC IR dipole B0APF with “optimum integral design” will be developed. This will include magnetic and mechanical analysis and a support structure likely consisting of stainless-steel tubes. Phase I will also demonstrate a short length (~150 mm), intermediate field (~2 T) proof-of-principle dipole with an aperture which will be close to the B0APF contemporaneous specifications. During Phase II, a proof-of-principle, full field dipole will be built and tested. The optimum integral design makes very short length superconducting dipole, quadrupole and other higher order multipole magnets possible that are not possible by other designs. This opens up new possibilities in the fields of accelerator, medical, defense and other applications. Demonstration of the “optimum integral design” with “direct wind technology” for short medium field superconducting magnets essentially eliminates the cost of expensive tooling such as needed for typical each conventional cosine theta magnets.

The length of most accelerator magnets is much greater than the diameter, and therefore the loss in effective length from the ends (about a coil diameter in dipoles) is relatively small. However, for short magnets, such as some envisioned for the Interaction Region (IR) of the Electron Ion Collider (EIC), the end effects of the conventional cosine theta design will result in a relatively large reduction in magnetic length. This proposal is for developing an alternate optimum integral design which significantly reduces the loss of effective length due to the ends. In the optimum integral design approach, the ends become an integral part of the magnet in optimizing the cosine theta current distribution, thereby creating a higher integral field for the same coil length. The more compact design is critical when available space is limited as in the EIC. As a part of Phase I, we ported and further developed the codes for optimizing the optimum integral design. The lower cost of direct wind technology allowed us to design, build, and successfully test a proof-of-principle 1.7 T, 114 mm aperture, 600 mm long, 2-layer superconducting dipole based on the optimum integral design, a significant feat for a Phase I program. The goal of Phase II will be to demonstrate the optimum integral design for EIC IR dipole B0ApF. This will be a 3.8 T, 114 mm aperture, 600 mm long superconducting dipole, which is well beyond what has been demonstrated with direct wind technology so far. The magnet will also meet the field quality requirements. It is an ambitious goal for an SBIR/STTR program but one that we believe can be achieved based on the strong performance of Phase I. Finally, we will examine the applicability of the optimum integral design to other EIC magnets and for other applications, such as medical and accelerator beam lines where compact, medium field superconducting magnets are required. A direct wind magnet based on the optimum integral design will create higher quality fields and have lower adverse end effects than conventional designs making it ideal for uses wherein space is at a premium. Demonstration of the direct wind magnet based on the optimum integral design is expected to provide a superior technical solution and reduce the cost of developing and building such magnets. These magnets should find widespread use in particle accelerators for research and medical applications.