Slow extraction from the SPS is essential for present and future Fixed Target beams in the North Area, and will be a key feature of the beam for the proposed Beam Dump Facility experiments like SHiP. The 3rd integer resonant extraction mechanism and accelerator components used to remove the beam from the accelerator intrinsically generate a few percent of beamloss, most of which is localised in the extraction channel in LSS2. The resulting activation, radiation dose to equipment and important restrictions on personnel doses in case of intervention are the main limitation on the number of protons that can be extracted per year. In addition, the extraction process is inherently sensitive to orbit stability, ripple in the SPS power supplies and beam structure, which produce detrimental frequency modulation in the spill and effectively increases the POT needed.
In this presentation we describe the features of the extraction mechanism and quantify the beamlosses and spill harmonic content. On this basis we extrapolate the activation levels and consequent operational restrictions in case of 4e19 POT per year, in the light of recent SPS operational experience. The required loss reduction factor, stability and spill quality are discussed, together with potential improvement directions for achieving the target flux.