SBIR-STTR Award

High-field (~5 T) bent-dipole (0.7 m radius) magnets are required as part of a 180-degree-bend beam-transport region in the high radiation areas of a planned Rare Isotope Accelerator (RIA). The requirements for these magnets can be met by using a novel coil design called the double-helix dipole (DHD). The double-helix approach offers a solution to the design of these curved magnets that is much more cost effective and reliable than can be obtained using conventional cosine-theta accelerator magnet designs. This project will demonstrate a bent dipole with double-helix coils, designed not only to meet the operating specifications but also to be suitable for use in the high radiation areas of the RIA. The method employs helical windings on composite or moldable ceramic coil forms, followed by an epoxy vacuum-impregnation process that creates the strong coil structure necessary for high field magnet applications. In Phase I, the magnetic and mechanical design concept for a radiation-hard bent dipole will be developed. The method of coil manufacture, involving composite or moldable ceramic tubes with vacuum-impregnation of epoxy, will be demonstrated by fabricating test coil sections that have the approximate cross section of the final magnet. The impregnation adhesive will be tested by thermally shocking the test coils and then examininng the interior to show that the adhesive does not crack or otherwise degrade. A demonstration dipole using this technology will be built and tested in Phase II.

Commercial Applications and Other Benefits as described by the awardee:
The bent double-helix magnets should provide an important contribution to accelerator magnet design for the RIA and other applications having similar requirements. For example, a bent solenoid magnet with superimposed dipole field is required in the cooling channel of a future Muon Collider. Another application of double-helix dipole windings, especially with the use of high temperature superconducting materials, is in the stators and rotors of superconducting electrical machines used to produce high power density motors and generators. Such devices would be of interest to government agencies such as DOD and NASA

High field superconducting dipole magnets, with a field strength of about 4.5 Tesla and a bend radius of about 0.7 m, are required in the high radiation areas of beam transport in future rare isotope accelerators. However, the small bending radii of these magnets produce unwanted higher-order harmonics in the magnetic field, which are detrimental to accelerator operation. This project will develop a novel coil design, the double-helix dipole, which provides an inherent ability to cancel unwanted higher order harmonics. The double-helix dipole employs helical windings on composite or moldable ceramic coil forms, thereby creating very robust coil structures, as needed for reliable superconducting magnets. Phase I designed a bent dipole magnet to meet the specifications of the planned Rare Isotope Accelerator (RIA). It was shown that the higher-order harmonics caused by the bending radius of the coil could be compensated by modifying the conductor path of the double-helix coils, thus allowing the magnet to meet field quality requirements. A manufacturing process for double-helix coils was developed, and two prototype coil windings were manufactured and shock tested with liquid nitrogen to qualify the constituent materials for cryogenic applications. During Phase II, two superconducting magnets will be manufactured and cryogenically tested at a national laboratory. The first magnet will be a short straight coil without iron yoke to qualify the superconducting cable and the manufacturing technology. The second magnet will be a prototype bent magnet with iron yoke. Field measurements will be performed at operational temperature, in order to verify the method of compensating for higher-order multipole components in the winding itself.

Commercial Applications and Other Benefits as described by the awardee:
The bent double-helix magnets should be an important contribution to accelerator magnet design for planned rare isotope accelerators. In addition, the high uniform field and the low manufacturing cost would make the technology an ideal fit for use in the field of proton therapy. The coil technology also should be suitable for use in rotors and stators of high power electrical machinery