RHIC Magnetic Measurements: Definitions and Conventions

This note describes the formalism and conventions used by the RHIC magnetic measurements group in defining and measuring the multipoles in magnets of various multipolarities, such as dipoles, quadrupoles, etc. Procedures are described for obtaining multipoles for tracking studies when the actual configuration of a magnet in the accelerator is different from that used in the measurements. Much of the information in this note can be found in earlier publications[1] and numerous Magnet Test Group notes by J. Herrera[2]. This note is an attempt to combine all the relevant information at one place, in a manner consistent with measurement and tracking conventions used at RHIC.