Development for large dynamical field range, wide good field region C-magnet

The dipole magnets are used frequently in the different types of accelerators. The solution of Laplace's equation was introduced to calculate the pole shape based on the assumption that the pole surface is the equal scalar potential surface if the permeability is high enough [1]. During the calculation of the pole shape, one usually uses the error function to describe the distribution of the magnetic field. However, we suffered some convergence problem in the solving process of the equal potential equation with the high order derivatives of the error function. In this paper, a new function is opted to describe the distribution of the field for the dipole. The solutions of the 3D Laplace's equation determined by the distribution from this new function are investigated widely. A dipole magnet with the resulting shape of the pole is designed by the numerical computation to confirm the performance of this new function and is fabricated based on such a design for the experiment study. The 2D and integrated field uniformity and the good field region are measured by Hall probe and search coils respectively. The measurement results are also presented.