Magnetic measurements on the ISR superconducting quadrupoles

The eight superconducting quadrupoles of the ISR high luminosity insertion were measured by the rotating coil method. This method allows an analysis of all harmonic components of the field. In order to achieve magnetic measurements precise enough to check the quality of the magnet, a study of the errors inherent in such a measuring system was made. This paper describes how the measurement of the different harmonics of the field is affected by imperfections of the mechanical or electronic components of the measuring system. Following this study, the relative errors of the gradient are measured within 0.2 10^-3in the useful aperture, the absolute value of the quadrupole term is known within 0.5 10^-3as a function of current, and the magnetic axis is determined within 20 microns. Results of the measurements show that by using the dodecapole correction winding, the relative error of the gradient integrated along the axis can be kept within the tolerance of 1‰ in the useful aperture of the magnets.