Prototypes of LEP Bending Magnets with Steel-Concrete Cores

In the large European electron positron storage ring project (LEP), the guiding magnets have a field of 0.123 T at the maximum energy of 130 GeV obtainable with superconducting RF cavities. To take advantage of these low field levels, steel-concrete cores with a steel filling factor of 0.27 are proposed. The magnets are excited by means of aluminium bars running along the circumference (Fig. 1). The design features and the experience gained with prototypes are given.