Operation of the CERN PS-Booster above 1 GeV: saturation effects in the main bending magnets and required modifications

The PS-Booster consists of four superimposed rings. The bending magnets are made from single yokes with four 'C'-type gaps. This geometry leads to an inherent asymmetry in the flux distribution around inner (II, III) and outer (IV, I) rings. From 1999 the PS-Booster is foreseen to be operated at the ejection/transfer energy of 1.4 GeV in view of LHC operation. The aim of this study was the investigation of saturation effects in the main bending magnets at energies above 1 GeV. It was found that the rather special yoke geometry leads to strong saturation around the outer gaps. This in turn causes a difference of nearly 1% in the bending fields between inner and outer rings at a beam energy of 1.4 GeV. This cannot be compensated with the existing BDL-correction system. To make the operation of the PS-Booster possible at 1.4 GeV, different solutions are discussed and the use of an additional trim power supply is proposed.