Development of a Field Mapper for the Determination of the Multipole Components of the Curved HESR Dipole Magnets

The high-energy storage ring (HESR) will comprise various normal-conducting magnets, in particular 44 dipole magnets each with a length of 4.2 m and a curvature providing the optimum good-field region for antiprotons with a maximum momentum of 15 GeV/c. All the dipole magnets have already been manufactured and delivered. For their quality control a field mapping device has been designed and built, which can be moved automatically along the curved central particle trajectory in order to measure the magnetic fields on a reference radius. From these data, we are able to extract the local multipole components at the required field strengths. Here, we focus on the design of this field mapper and present an example of a field measurement, which will be applied to a subset of the HESR dipole magnets.