Capture Losses Caused By Intensity Effects In The Cern Sps

The CERN SPS machine has been extensively upgraded to prepare it for its future role as the LHC injector. These changes include a significant impedance reduction programme and new beam-control and feedback systems. Nominal beams have recently been produced at the extraction energy, 450 GeV. To achieve this intensity it was initially necessary to inject higher intensities due to particle loss at capture and low energy. These intensity-dependent losses reached 30% for matched, but not optimum, capture. Studies of different phenomena leading to these losses have increased the transmission efficiency to similar to 95%. We describe the steps taken to minimize losses, pointing out mechanisms involved and presenting unresolved issues.