Field Measurements of the ATF2 Quadrupole Magnets Manufactured by IHEP

ATF2 (Accelerator Test Facility 2) is an international project designed for testing the final focus system that is envisaged at ILC. The primary project goal is to establish the hardware and beam handling technologies pertaining to transverse focusing of the electron beams to nearly 40 nm. The beam is extracted from the existing ATF ring to the new ATF2 beam line and brought to the final focus point which is about 90 m downstream of the extraction point. There are 43 quadrupole magnets in the ATF2 beam line, of which 28 (27 1 spare) are of the same type and were manufactured by Institute of High Energy Physics (IHEP), China. The tolerances on higher-order multipole components are tight, especially for the sextupole component. Magnetic field measurements with a harmonic coil were carried out on these quadrupole magnets at KEK and the integrated strength, the horizontal and vertical magnetic centers, median plane position and the higher-order multipole components were measured. The measurement results are summarized in this report.