Conclusions from Recent Pionic—atom Experiments

The most recent pionic-hydrogen experiment marks the completion of a whole series of measurements, the main goal of which was to provide conclusive data on pion-nucleon interaction at threshold for comparison with calculations from Chiral perturbation theory. The precision achieved for hadronic shift and broadening of 0.2% and 2%, respectively, became possible by comprehensive studies of cascade effects in hydrogen and other light exotic atoms including results from the last years of LEAR operation. In order to obtain optimum conditions for the Bragg crystal spectrometer, the cyclotron trap II has been used to provide a suitable X-ray source. To characterize the bent crystal spectrometer, the cyclotron trap has been modified to operate as an electron-cyclotron resonance source, which produces with high intensity narrow X-ray transitions in the few keV range originating from highly charged ions.