Measurement of transverse beam emittance of split beams for the CERN Proton Synchrotron Multi-Turn Extraction

Crossing a horizontal nonlinear resonance is the approach that can be used to split a beam in several beamlets with the goal to perform multi-turn extraction from a circular particle accelerator. Such an approach has been successfully implemented in the CERN Proton Synchrotron and is used routinely for the production of high-intensity proton beams for fixed-target physics at the Super Proton Synchrotron. Recently, thanks to the deployment of diamond detectors, originally installed to monitor the beam losses at extraction, it has been possible to measure the horizontal beam emittance of the split beam just prior to extraction. This is the first time that an emittance measurement is attempted for split beams, i.e. in a regime of highly nonlinear beam dynamics. In this paper, the technique is presented and its application to the analysis of the experimental data is presented and discussed in detail. This result is essential for the performance assessment of the splitting process and for the design of further performance improvements.