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Abstract

In this work measurements of the total cross section for the ionisation of cesium atoms in collisions with highly charged ions (Cq+, q=3, 4, 5, 6 und O8+) at energies of some MeV/u are presented. The cesium atoms are confined in a magneto-optical trap, which is installed inside the Heidelberg Test Storage Ring TSR. Additionally, the transfer of electrons from the target atoms to the stored ions (C4+, C6+, O8+) is investigatetd. Inner shell vacancies produced in the capture process are filled by Auger-cascades and shake-off processes leaving the cesium ionized to several charge states. The charge states are resolved by time-of-flight (TOF) measurements. From the TOF spectra an estimation for the transfered momentum to the recoil ion can be made. As an additional application the ultracold atom cloud is used as a probe to measure the transverse density distribution of the stored ions very precicely. This method is of great interest for very dilute beams because reliable measurements down to very low ion currents in the order of 10 nA become possible. The resolution of this method is only limited by the size of the atom cloud (actual diameter: some 100 µm) and is better than the resolution of the restgas beam profile monitor.