Single differential projectile ionization cross sections d$\sigma $/dE$_{e}$ for 50 AMeV U$^{28+}$ in the ESR storage ring

The very high intensity beams of relativistic high Z ions with incident collision energies up to 2.7AGeV requested for experiments using the SIS100 synchrotron of FAIR require that 1.3 10$^{11}$ ions at 2.6Hz be injected from SIS12/18 into SIS100. The needed luminosity of the beam can only be achieved for such high Z ions when - considering the space charge limit ($\sim $A/q$^{2})$ - a low charge state q of the ion to be accelerated keeps the particle density at the highest feasible level. For a thorough understanding of beam loss it is imperative that the mechanisms active in projectile ionization be understood quantitatively to provide benchmarks for advanced\textit{ ab initio} theories beyond first order. We have embarked on an experimental investigation of single differential projectile ionization cross sections d$\sigma $/dE$_{e}$ (SDCS) for single and multiple ionization of U$^{28+\, }$in the ESR storage ring by measuring the electron loss to continuum (ELC) cusp at 0$^{0}$ with respect to the beam axis employing our imaging forward electron spectrometer. This was motivated by the high relative fraction of multiple ionization estimated to exceed 40{\%}. We report first results for absolute projectile ionization SDCS for U$^{28+}$. We find a remarkably high asymmetry for the ELC cusp. This is at strong variance with the line shape expected for validity of first order theories.