Progress with the Upgrade of the SPS for the HL-LHC Era
  The demanding beam performance requirements of the High Luminosity (HL-) LHC project translate into a set of requirements and upgrade paths for the LHC injector complex. In this paper the performance requirements for the SPS and the known limitations are reviewed in the light of the 2012 operational experience. The various SPS upgrades in progress and still under consideration are described, in addition to the machine studies and simulations performed in 2012. The expected machine performance reach is estimated on the basis of the present knowledge, and the remaining decisions that still need to be made concerning upgrade options are detailed. 
B. Goddard, T. Argyropoulos, H. Bartosik, W. Bartmann, T. Bohl, F.   Caspers, K. Cornelis, H. Damerau, L. Dr{\o}sdal, L. Duc...
physics.acc-ph