New method to design magnetic channels with 2D optimization tools and using permendur vanadium

Magnetic channels are used in almost all cyclotrons to focus radially the beam along the extraction path through the coils and yoke region, where the rapid fall off of the magnetic field produces a strong vertical focusing and radial defocusing of the beam. These magnetic channels consist generally of three iron bars. The current sheet approximation has been generally used to evaluate quickly the performance of magnetic channels. For the new magnetic channels to be used in the upgrade of the LNS-INFN k800 Superconducting Cyclotron, a new method was developed to investigate complex configurations and to achieve higher magnetic gradients in a larger area. The optimization procedure is based on a genetic algorithm implemented on MATLAB code and using the COMSOL code to perform the 2D magnetic field simulations. Moreover, the use of permendur vanadium in alternative to iron allows to reduce the volume of the bars and mainly the magnetic force. The results of our simulations are here presented.