A pulsed elliptical quadrupole array for transport of multiple high current beams

We present the design of a pulsed quadrupole magnet array for side by side transport of multiple high current particle beams in induction linear accelerators. The design is directly applicable to low field superconducting quadrupole arrays and can be modified for high fields. The magnetic design minimizes current requirements by placing a modified cosine 2θ current distribution inside an elliptical iron boundary. The resulting magnet aperture more closely matches the beam´s elliptical cross-section, and only the space the beam occupies is magnetized to the required field quality. By eliminating unneeded high field area in the magnet aperture, energy requirements are halved, as compared to an equivalent circular design. The magnet serves double duty as a UHV vacuum chamber/beam tube, and reduced radial thickness results from lower current requirements. Each interior magnet´s neighbors serve as the return flux paths and the poles are placed as close as possible to each other to facilitate this. All the above features serve to reduce the beam-to-beam spacing, leading to significant reductions in the size and cost of the induction cores which surround the array, as well as the pulsed power supplies which drive them. The design shown here is for a 21 beam array, yet it is suitable for larger or smaller numbers of beams, as required