Experiment Geneva Saclay on the M13 beam Experiment S124

Images show the K-meson spectrometer of the Geneva-Saclay collaboration being dismantled for use in the experiment S 124. This apparatus included: proportional wire chambers, spark chambers, an analysing magnet, two multiple-cell Cerenkov counters and three scintillator hodoscopes. It was by means of this spectrometer, which is used for studies of the K⁺ → π⁺ π⁻ e⁺ v decay, that the very rare channel K⁺ → π⁺e⁺e was discovered.