Chromaticity modelling in the Fermilab Main Ring

As computer simulations of accelerators improve, it becomes important to measure the properties of existing machines better to verify that the simulations are indeed accurate. The Fermilab Main Ring magnets are known to be rich in harmonic content, but they were not individually measured. The authors have measured the nonlinear dependence of tune vs. momentum error and they interpret these data in terms of the octupole content of the main quadrupoles and the decapole content of the dipoles.<>