STORAGE RING MAGNET OF THE 3RD MUON (G-2) EXPERIMENT AT CERN

The third (g-2) experiment carried out at CERN required a storage ring magnet with a field as uniform as possible and known with an accuracy of a few parts per million over the whole storage region. Here we describe this magnet, which has a useful aperture of 120 mm horizontally and 80 mm vertically and a diameter of ∼14 m. The various field controls necessary are indicated, and the complex procedure adopted for the shimming work is described. The finally reached homogeneity of the field, averaged in azimuth, was 3 ppm. All the various error sources and field map corrections needed are analysed. Finally, the special aspects of the machine developed for the shimming are described. © 1979 North-Holland Publishing Co.