Wiesel, Marco (2017)
Preparation and Investigation of Highly Charged Ions in a Penning Trap for the Determination of Atomic Magnetic Moments.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

The ARTEMIS experiment aims at measuring magnetic moments of electrons bound in highly charged ions that are stored in a Penning trap. It will provide access to effects of quantum electrodynamics (QED) in the extreme fields close to an ionic nucleus. Additionally, due to the high magnetic field of the Penning trap, higher-order Zeeman effects can be examined and therefore provide a different access to the theory of QED. In this work, a cooled cloud of boron-like argon ions, Ar13+, was prepared in the creation part of a double Penning trap held at cryogenic temperatures. Systematic measurements were carried out in order to investigate the creation trap and its specific parameters to generate a suitable ion cloud. This ion cloud consisted after further charge breeding of different charge states. It was then cooled and parts of it were excited by the SWIFT-technique and, in combination with fast potential-switching, all ion species except Ar13+ were removed. Together with the successful transport of an ion cloud from the creation trap into the spectroscopy trap all concepts necessary in order to prepare an Ar13+ ion cloud for performing laser microwave double-resonance spectroscopy have been implemented. Additionally, a measurement of the modified cyclotron frequency in the creation trap was carried out by exciting the ions radially while detecting their axial motional frequency. Thus, a value for the magnetic field strength in the creation trap with a 5 parts-per-million accuracy was achieved. A system for irradiating microwaves with a frequency of 65 gigahertz onto the position of the ions was developed, characterized and implemented into the apparatus. It was conceptualized for meeting the challenging conditions of the experiment, such as the high magnetic field, the cryogenic temperatures and the difficult geometry. A novel concept of employing an indium tin oxide (ITO)-coated window as an endcap for a closed Penning trap was implemented in the spectroscopy trap and its functionality was proven. The window improves the fluorescence photon efficiency by at least 17% and increases the planarity over the previously used mesh and therefore decreases the trap anharmonicities. Additionally, a test of the ITO-coated window proved its applicability as a Faraday cup for detecting highly charged ions. During this thesis, experimental studies of the various components of ARTEMIS have been carried out and the full apparatus was assembled and put into operation. The focus of this work was the design of the mechanical parts and their assembly, such as the cryogenic concept and the vibrational decoupling. In the future, ARTEMIS will be connected to the HITRAP beamline at GSI, so heaviest highly charged ions can be examined. During this work, a fast opening valve, that separates the trap vacuum from the beamline vacuum, was assembled and initial tests were conducted.

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