CHARGE-EXCHANGE CROSS-SECTIONS AND BEAM LIFETIMES FOR STORED AND DECELERATED BARE URANIUM IONS

Charge-exchange cross sections and beam lifetimes are studied for dece lerated bare uranium ions at the ESR storage ring. By deceleration fro m the initial energy of 358 MeV/u down to various energies as low as 4 9 MeV/u, i.e., far below the production energy of bare ionic species, the electron pickup cross sections were obtained for collisions with N -2, Ar, CH4, and Kr gaseous targets. The measured cross sections and b eam lifetimes are compared with the theoretical results for radiative and nonradiative electron capture. The present data, along with the th eoretical approximations discussed, provide a solid basis for the esti mation of beam lifetimes for decelerated bare high-Z ions. Moreover, a normalization procedure is proposed, in which absolute total charge-e xchange cross sections are derived by normalizing the simultaneously m easured yield of radiative electron capture photons to rigorously calc ulated relativistic cross sections. This method, along with the unprec edented beam conditions at the ESR storage ring, allows a significant improvement of the accuracy of cross-section data.