Dipole Field, Tune and Chromaticity Correction at the SPS: from Converter Tracking to Eddy Currents

Good control of key parameters like dipole field, tune and chromaticity is a basic requirement for fast cycle commissioning and for good beam transmission through the SPS ramp. The reproducibility of those parameters depends on power converter tracking, eddy currents and remnant fields. The new SPS control system was used to study some of the problems in the low energy ramp segment of the fixed target beam. A small modification of the function generation for the main converters is shown to reduce residual converter tracking errors by more than one order of magnitude. Tune and chromaticity corrections have been analyzed and summarized for different cycles, both for the ramp as well for the injection plateau where eddy current may play a significant role.