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Collinear laser spectroscopy in the 1s2s³S₁→1s2p³P₀,₂ transitions of helium-like ¹¹B³⁺ was performed using the HITRAP beamline at the GSI Helmholtz Centre. The ions were produced in an electron beam ion source, extracted, and accelerated to a beam energy of 4 keV/q. Results agree with previous measurements within uncertainty. Thus, it was demonstrated that the metastable state in He-like ions is sufficiently populated to carry out collinear laser spectroscopy. The measurement is a pilot experiment for a series of measurements that will be performed at a dedicated collinear laser spectroscopy setup at TU Darmstadt with light helium-like ions.

Today, quantum electrodynamics (QED) is considered the most precisely tested theory in physics. The most precise tests have been performed mainly on comparatively simple systems such as the free electron. However, since QED should also be valid in the most extreme electric and magnetic fields, according to today’s understanding, tests must be performed in this regime as well. Heavy and highly charged ions are suitable for this purpose, because the remaining electrons near the nucleus are exposed to these extreme fields. Since such ions do not occur naturally on earth, they must be produced artificially. This requires high energies and, especially for the heaviest elements, large accelerator facilities, such as the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. In this work, laser spectroscopy of artificially produced ²⁰⁸Bi⁸²⁺ at relativistic energies was performed at the storage ring ESR of GSI. This is the first time that in-flight produced ions have been successfully studied by laser spectroscopy in a storage ring. The main challenge is the small amount of ions, which leads to low signal count rates in the detectors. In part due to the data analysis performed in this work, the measured background has been reduced to a point where the energy difference of the hyperfine splitting can be extracted. The obtained result is ²⁰⁸∆E⁽¹ˢ⁾ = 5598.97(1)(8) meV and represents an important milestone for the test of QED in the strongest magnetic fields. The accuracy of laser spectroscopy in storage rings like the ESR is limited by the velocity distribution of the ions. To improve the accuracy by several orders of magnitude, ion traps can be used. However, it is not possible to directly capture ions produced at relativistic energies in an ion trap. Therefore, in the second part of this work, the Cooling Trap of the HITRAP facility was commissioned. The task of the HITRAP facility is to decelerate the highly charged ions, to cool them and to transport them fur

Highly charged heavy ions at rest offer a wide spectrum of precision measurements. The GSI Helmholtzzentrum für Schwerionenforschung GmbH is able to deliver ions up to U92+. As the production of these heavy, highly charged ions requires high kinetic energies, it is necessary to decelerate these ions for ultimate precision. The broad energy distribution, which results from the deceleration in the HITRAP linear decelerator, needs to be reduced to allow for further transportation and experiments. The HITRAP cooling trap is designed to cool, i.e., reduce, this energy spread by utilizing electron cooling. The commissioning of this trap is done with Ar16+-ions from a local EBIT ion source. By analyzing the signal of stored ions after ejection, properties such as ion lifetime, charge exchange, and ion motions can be observed. Here, we provide an overview of the recent results of the commissioning process and discuss future experiments.