Study of electron bremsstrahlung in strong Coulomb fields at the ESR storage ring

Electron bremsstrahlung has been investigated for collisions of 223.2 MeV/a mu He-like uranium ions with N-2 and Ar gaseous targets. The doubly differe ntial cross-sections for bremsstrahlung are compared to the predictions of relativistic first order Born calculations (Bethe-Heitler formula with Elwe rt correction factor) and to the calculations based on the exact wavefuncti ons for electrons moving in the external point-Coulomb potential of the pro jectile. Whereas the "exact" IPA calculations give an improved agreement wi th experimental data, as compared to the Bethe-Heitler theory, in particula r at the end-point region of the bremsstrahlung spectra, discrepancies stil l remain at lower photon energies.