Analog Computer for Quadrupole Magnet Design

In the design of particle accelerators, magnets are sometimes used to bend the paths of charged particles in linear accelerators for focusing and defocusing purposes. These magnets, in the present case, are known as quadrupoles. Their design hinges on the solution of certain mathematical expressions of particle trajectories. A computer of the analog type was constructed to solve the equations and so facilitate magnet design. The analog computer for this application has dials labeled "L", "μ", and "θ". The settings of these dials represent the design parameters under study. The operator can set the dials of each stage to any of thousands of different combinations of L, μ, and θ. The results of his settings may be observed on a CRO screen. He can then proceed to search for the best combination of control settings with regard to their effect on particle trajectories. Once having found a satisfactory combination, the corresponding magnet design parameters are obtained from the settings of the controls. Three features of construction required special consideration. These were: the high gain, minimum phase shift, and minimum crosstalk. These items and others are discussed in the article from the practical as well as the theoretical point of view.