Control of the Michigan State University Cyclotron

To operate the MSU cyclotron, controls are set to pre-computed values prepared by a computer program known as SETOP; to obtain a complete set of operating instructions the experimenter need only specify the particle of interest and a field identification number roughly proportional to energy. The program uses this information along with measured field data and a pre-computed set of ideal fields to determine the desired "operating point" in a straightforward series of calculations: (1) the fields at the desired excitation are synthesized by interpolation in the measured field data, (2) an average field is obtained using a modified least squares fit of the desired average field by the trim coils, and (3) the rf frequency is determined so as to minimize the energy spread of the beam in a single turn at the extraction energy. This paper describes the procedure used in SETOP to determine such operating points, and discusses the principle features of these computations. A typical SETOP sheet is presented along with instructions for its use. Results of beam measurements are in excellent agreement with computed beam behavior.