Simultaneous Slow Resonant Extractions from the SPS with Horizontal Tune-Split

With the upgrading of the West experimental area it became necessary to extract protons at 450 GeV/c simultaneously towards two experimental zones. However, the corresponding extraction systems are at locations which, when the normal periodicity is maintained, would not allow this procedure. During the time of extraction, the horizontal tune has therefore to be split unequally between two halves of the machine circumference such that the betatron phase difference between the electrostatic septa of the two extraction systems becomes a multiple of 2¿. The separatrix then being the same at both septa entrances, the sharing ratio can easily be adjusted by changing the radial position of the circulating beam relative to the first septum with a compensated bump.