Performance of the PEP-II Low-Energy Ring quadrupoles

Production quantities of quadrupoles for the PEP-II Low-Energy Ring (LER) have been fabricated and measured in China in collaboration with IHEP (Beijing). The LER design specification calls for short quadrupoles (L_eff=430 mm) with a bore radius of 50 mm. End effect corrections, using a chamfer geometry originally developed for the ALS quadrupoles at LBNL, were verified in a prototype magnet prior to release of the design for production of the 320 quadrupoles (including spares) required for the LER. Rotating coil measurements were carried out at IHEP yielding multipole error spectra, magnetic center distribution and transfer function behavior for the full production quantity of magnets. Separate measurements were made to determine the reproducibility of magnets connected together in a series string by measuring the individual magnets against a reference magnet using a bucking magnet. Measurement results of all the magnets indicate that the error multipole spectra satisfy the field quality requirements, reproducibility requirements for magnets in a power supply string are satisfied and the spatial distribution of the magnetic center with respect to the mechanical magnet center falls within a radius which is substantially smaller than the transverse alignment tolerance specified for the quadrupoles