Magnet-field design considerations for a high-energy superconducting cyclotron

This paper reports the pole shape designs for a two stage superconducting isochronous cyclotron combination (CANUCK) to accelerate 100 ..mu..A proton beams to 15 GeV. The pole shape of the 15 sectors of the first stage 3.5 GeV proton cyclotron provides isochronism over the full energy range and a constant axial tune over all but the lowest energies. Progress on the pole design of the 42-sector 15-GeV second stage is also reported. The magnetic fields are computed from the current distribution of the superconducting coils and the infinitely thin current sheets simulating the fully saturated poles. A least-squares method is used to minimize deviations from isochronism by adjusting the size of various elemental shim coils placed around the main coil. The method to obtain the desired axial tune is described. 13 references, 6 figures.