Upgrade of the 200 MHZ RF System in the CERN SPS

The 200 MHz RF system used in the SPS for acceleration of all beams including the LHC-type ones has a travelling wave structure and consists of four cavities, two of them with five sections and two with four. For stability of future high intensity LHC beams in the SPS larger (than now) controlled longitudinal emittance blow-up and therefore bucket and voltage amplitude will be necessary, but less voltage will be available due to the effect of beam loading in the existing system with maximum peak RF power per cavity of 1 MW. This issue will become critical for beam acceleration and especially for beam transfer into the 400 MHz RF system of the LHC. The proposed solution is to shorten the two long cavities and using free sections together with two spare to install two extra cavities with corresponding power plants of 1.4 MW each. After this upgrade, which is a main part of more general SPS upgrade for high luminosity LHC and should be completed during 2017, the performance of the SPS RF system with high intensity beams will be significantly improved and at the same time the overall peak impedance of the system will be reduced by 20%.