Title: A simple class of beam transport systems with optically axisymmetric transfer properties
Abstract: It is demonstrated that for quadrupole-beam transport systems that have a specific symmetry, two of the three conditions that have to be satisfied in optically axisymmetric systems are automatically fulfilled. These systems therefore need to have only one free parameter to make them optically axisymmetric, and the resulting design formulas are presented and discussed. As a generalization, it is shown how dipole magnets, solenoids, or electrostatic elements can be included in the optical train. A system with lower symmetry, requiring adjustment of two parameters to achieve optical axisymmetry, is also described.