Upgrade of the CERN Proton Synchrotron Booster bending magnets for 2 GeV Operation

Since its first operation in 1972 at an energy of 800MeV the CERN Proton Synchrotron Booster, which consists of 4 super imposed synchrotrons, has seen two upgrades: once to 1.0 GeV in 1988 and then to 1.4 GeV in 1999. During this time the main magnets of the machine have remained largely unchanged with small differences (<1%) between the inner and outer gaps of the main bending magnet fields being compensated by trim power supplies. The future upgrade of the machine will demand to extract protons at an energy of 2.0 GeV and require almost double the original dipole field. At this field, due to saturation effects, the inner and outer gaps of the main dipole magnets will differ by up to 4%. This paper presents the design and implementation of a modification of the magnetic circuit strongly reducing these effects. We also discuss the results of experimental tests concerning the effects on field quality and eddy current transients, including the implications for the real-time magnetic field measurement system to control RF and power supplies.