The design of the accelerating cavity for SuSe with the aid of the three-dimensional cavity calculation program CAV3D

SuSe is a project study at the Munich Accelerator Laboratory for a superconducting sector cyclotron to access the medium energy range up to 300 MeV/u for heavy ions. The RF-system for SuSe consists of two large cavities in opposite valleys. The cavities are driven in the TE 101-mode and have a radially increasing voltage distribution, The frequency can be tuned in a wide range between 59 MHz and 74 MHz by movable acceleration lips and two plunge tubes. It was a difficult task to find a cavity geometry that fits into the narrow place between the SuSe-magnets and has a high enough voltage at the injection-radius of o.4 m, a large frequency range and the best possible shunt impedance. A very valuable tool for optimizing the cavity geometry was the three-dimensional cavity calculation program CAV3D2, together with model measurements. CAM calculates the frequency, voltage distribution, Q-factor and electromagnetic fields of low modes of arbitrarily formed three-dimensional cavities with an accuracy of several percent.