Development of quadrupole arrays for heavy-ion fusion

Extensive studies have been performed to optimize the design of superconduc ting quadrupole arrays for beam transport in future heavy-ion fusion accele rators. In these arrays, 20 or more quadrupole coils are densely packed wit h their axes aligned in parallel. Field strengths between 3 and 5 tesla at the inner coil diameters have been investigated. The aperture of the indivi dual quadrupoles has been varied between 60 mm and 240 mm. The coils have a typical length of 1 m, and special effort has been made to minimize the le ngth of the interconnect region between the array and adjacent accelerator components. The relative orientation of quadrupoles in the array is chosen to optimize field sharing between neighboring cells. In the presented desig n, field uniformity in the boundary cells is maintained by placing concentr ic correction coils onto these cells. A novel approach for the mechanical s tabilization and alignment of the individual quads in the array has been de veloped. Since Inertial Fusion Energy has to compete with other long-term energy sou rces, cost and reliability are major issues of the magnet array. The presen ted design uses a round NbTi mini-cable, which allows for a cost-effective, highly automated manufacturing of the required superconducting coils. A fl exible, 37-strand mini-cable has been developed and prototype manufacturing has started.